Leaf Bronzing/Burning + Twisted Leaves

[IllusionalFate]

About a week ago I went on vacation, and came home to find out that the light cycle was delayed 4 hours due to a power outage. The leaves were thinned out and wilting, the stems were floppy and weak, there was some "bronzing" occurring on one of the leaves, and some dead/dying leaves near the bottom.

I watered them with FoxFarm Grow Big and two drops of superthrive mixed in when I got home, and for the most part they have seemed to recover. I doubt they were overdosed with nutes since I watered them with only plain water before leaving and the last time I gave any nutes was about 5 days before that.

Plants are 5 weeks into veg, are under a 600W metal halide that is 15-18 inches away from the top of the plants, and soil is FoxFarm Ocean Forest which has a PH level of 6.8-6.9 right now. Temps range from 77-90 degrees during lights-on, and 62-70 during night periods.

What could be causing this stress?

EDIT: I just read that "Thin, shrivelled leaves can be from low humidity." Since about 1/4th of the leaves, almost all are near the top of the plant, are curling into a "U" shape and since the leaves feel dry even though they're not fading in color I think this is most likely the problem. The humidity stays mostly around 15-20% which I know is very low, but the 600W metal halide just completely KILLS the humidity in the room. How other people use HID lighting and keep humidity at a good level without any additional humidifying devices is beyond me.

 

[Ilikebigbuds]

here's what I found in my MJ Bible- page 250

Phosphorus(P) -

A lack of phosphorus causes a stunted growth and smaller leaves; leaves turn bluish-green and blotches often appear. stems, leaf stems and main veins turn reddish-purple starting on the leafs underside. note: the reddening of the stems and veins is not always well pronounced. the leaf tips of older leaves turn dark and curl downward. severely affected leaves develop large purple-black blotches. these leaves later become bronzish-purple, dry, shrivel up contort and drop off.

treat deficiency by lowering PH to 5.5-6.5 for potting soild so phosphorus will become available. if the soil is too acidic, and an excess of iron or zinc exists, phosphorous becomes unavailable.

use bat guano, steamed bone meal, natural phosphates, or barn yard manure- to add phosphorous to soil.

treat toxicity by flushing the growing medium with a very mild and complete feterlizer. severe problems will require more water to be flushed through the growing medium. flush a minimum og three times the volume of water for the volume og the growing medium.

- if you want more infor on this let me know.

I'm just getting this info from Jorge Cervantes - MJ grow bible.

hope this helps.

 

[HippyInEngland]

Hi I F

Your problem could well be this ....

Boron (B) Micronutrient and Immobile element

Boron is important when dealing with maturation, pollen germination and seed production. As well as keeping calcium in soluble forms and keeping the stems, stalks, branches strong. Boron keeps good colour on the leaves and helps produce the plants structure. Boron also aids in cell division and protein formation.

Boron deficiencies will show up first in younger leaves (they may turn yellow), then moves up the plant. Boron deficiency can resemble calcium deficiency. Stunting, discolouration, possible death of the growing tips, bud abortion and development. The Roots will show a stunted with swollen short secondary roots, leaves distorted, sometimes bronzed or scorched.

 

[IllusionalFate]

Thanks for the replies!

Both those describe symptoms of my plants and it looks like the problem could be either. These are the similarities with my plants:

Phosphorus deficiency:
-Leaves are bluish-green at the tips
-Growth seems to be progressing unusually slowly for the last week and a half
-dying leaves

Boron deficiency:
-Young leafsets are yellowish
-stunted growth
-bronzed/scorched leaves

Do you really think any of these nutrients could be locked out with a PH of 6.8? I thought that was within the safe zone for soil growing.

 

[HippyInEngland]

Ok lets look at it from a different angle, you say your PH is 6.8, how are you checking this?

 

[IllusionalFate]

I check my PH using this:
hxxp://www.planetnatural.com/site/ph-meter.html

I know it's not near as good as a digital PH meter, but I think the results are probably still accurate enough.

 

[HippyInEngland]

Read this ...

http://www.marijuanapassion.com/forum/showthread.php?t=27943

Im not saying that is your problem, but could be, something else is on my mind, I presume your checking the water after you put the feed in it, also do you check the water run off incase your medium is altering the PH once it is in the soil?

 

[IllusionalFate]

I suppose I could have an inaccurate reading, but even if so I'm not using any product to alter the PH. I have a soil PH meter so I just stick the probe into the soil for it to register the PH.

Still, I don't understand why PH needs to be monitored. If PH is off doesn't that mean you're doing something wrong, or using a product you shouldn't be? I assume PH can't be off unless something is added to the soil to change the PH, and if certain nutes are too acidic or alkaline then why even use them?

 

[HippyInEngland]

I suppose I could have an inaccurate reading, but even if so I'm not using any product to alter the PH. I have a soil PH meter so I just stick the probe into the soil for it to register the PH.

Still, I don't understand why PH needs to be monitored. If PH is off doesn't that mean you're doing something wrong, or using a product you shouldn't be? I assume PH can't be off unless something is added to the soil to change the PH, and if certain nutes are too acidic or alkaline then why even use them?

Chemical reactions cause things to alter, something is causing your problem, if everything is correct in your mind, something outside is causing it, you can have a water ph of 7.6, you can and very often happens, add nutes and the PH alters, you then put this altered PH water in your soil and the soil then has its own chemical reaction and alter the PH even further, try this ...., check your water PH, then check it again after you add your nutes, then place the plant in its pot on a plate and slightly over water/feed your plant so the feed water drips out the bottom of the pot and collects on the plate (by the way, can you see roots from the bottom of the pot?) leave the plant for a couple of hours on the plate, then collect the 'run off' and measure its PH yet again, see if its altered

 

[IllusionalFate]

Ah, so even if you are using products that will normally not mess with your PH there can always be something that can cause it to go out of whack and make it worse further down the road. I will test the run off next time I water/add nutes and also test the PH of my tap water and nute solution.

 

[IllusionalFate]

I added nutes today and here are the readings:

Tap water: 6.9
Water with nutrients: 6.8-6.9
Run off: 6.8-6.9

No roots are coming out of the bottom of the pot.

The new growth so far has all looked healthy, no burning/yellow/bronzing, but there are still a couple twisted leaves in areas. I'm thinking the original problem had something to do with low humidity (the humidity has since gone up to 25%) and/or high temps (was in the 80s-90s when I was on vacation).

 

[HippyInEngland]

Let us know how its growing in a week