Nute burn or Phosphorus deficiency???

Please help! Do I flush or add fresh water? This has happenned today, and it looks like it is getting worse. The bottom and the top leaves look normal.

Ok, here is what I think happenned... When I added water a few days ago I tested everything. The PH was like 5.5 or close to it, the PPM was right around 350 (I am using FF Grow Big).
I am using an aeroponic system and I did not have all the light leakages covered and noticed some algae growing in the system. I cut Mylar and custom fit the top so they would die off. Apparently when the algae started dying, not only did it raise the PH to over 7, it also made the PPM go over 600 :O
I have the system back to the normal specs now, and I will just wait it out.

Am I correct in thinking that the dying algae caused these changes?

Usually dying algae wouldn't cause the pH to rise. The pH rises becuase of the nutes getting used. So, if there was more algae, the pH would rise even more. It may be that you are checking your numbers too soon after adding your nutes. I usually check mine an hour after tweaking. Here's a scenario, you add your nutes and you check your ppm and pH. The water gets some to mix and move around and really you didn't get a good read on your water because of that.... See what I'm saying?

Just to give you an update, they are looking much better and have not really slowed down from what I can tell... However when I changed everything out, I checked the PH and it was 5.5-6 (yesterday) and today it was OVER 7!!!

Apparently there was a LOT of algae, and since they eat nutes, they sucked up a bunch over the last few weeks and when they died, they released it back into the system... Which might explain why the PPM was so high. The PPM is now at 350, which is 50 higher than yesterday after I changed it.

Perhaps when a LOT of algae dies, their decaying little asses can acidify, causing the PH to rise drastically... Coupled with the release of nutes "all of a sudden" might explain it.

Until it died, the algae did not hurt the plants one bit. Although it was a bit of a shock to them, they are getting better by the hour. Big Bud is a very resilient strain... I like it so far

Algae and root growth will put ph up.... when the plants start regulatiing their growth water levels will drop faster then the nutes.. and u'll have the classic hydro falling ph values.

You also should test your water for hardness and cArbonate levels. If you are using RO water like I do, you have very suceptable water to ph rise and fall as nutes are added, as there is little buffering as you find in tap water. Ph is critical to your system, and stable ph is the most important thing you can do right now to begin to create a stable system. From there, if any problems arise, you can at least eliminate the ph.
Gil

Whenever leaves yellow or brown the most common thing to think is “nute burn!” However, there are other reasons for the leaves going yellow in the particular way that yours have. For instance, nitrogen deficiency.

I’m not familiar with the fert that you mention, but your ppm at 350 doesn’t sound too high to me. If anything, it sounds too low. I’m used to my reservoir being at anywhere from 700 to 1200 ppm, more if I’m generating CO2. So 350 ppm could be a sign that the NPK of your basic fert is not high enough, especially in Nitrogen.

I presume you’re in the veg stage, judging from the picture. Flushing your system is always a good idea, but if your plants are Nitrogen deficient, then you have to add a fert that has adequate supplies of Nitrogen, in order to have your plants grow green, luscious leaves.

I personally use the Advanced Nutrients 2-part, Sensi Grow A&B during my veg stage. In addition to my basic fert, I also mix in root colonizers, vitamins, and other supplements, including Grandma Enggy’s Humic Acid and Fulvic Acid.

These last two ingredients simulate the rich, black, organic topsoil that has been the secret of horticulturalists for centuries. Derived from a calcified organic substance known as “leonardite,” Humic Acid and Fulvic Acid supply a whole array of organic substances that aid in the healthy growth of plant tissues.

Another mistaken idea that you have is that the higher your pH goes the more acidic your reservoir gets. It’s exactly the opposite. The lower your pH, the more acidic the solution. You mention that your pH goes from 5.6 to 7, which is neutral. Anything above 7 is too alkaline. 5.6 pH is the desired level you should be aiming at.

How do you correct your pH? Advanced Nutrients makes two excellent products, pH Up and pH Down, which should be added in minute quantities to your solution, if the number needs correction.

Another participant commented that perhaps you take your readings too fast, and he’s probably right. After you mix all your ingredients, you should take a pH reading every half hour in order to determine when your solution has stabilized. Once it has, then you can feed it to your plants.

So you seem to have a lot of variables to consider before you can diagnose your problem as nute burn. Marijuana requires high levels of Nitrogen during vegetative growth, lower levels during flowering. Nitrogen, being mobile, is easily washed away and must be replaced regularly.

Nitrogen helps your cannabis plants to regulate the manufacture of proteins that are essential for creating new protoplasm in the cells. It is also essential for the production of chlorophyll, enzymes, alkaloids, amino acids, and nucleic acids, which are in turn irreplaceable ingredients in healthy plant cell production.

If you switch to a better fertilizer, such as the ones made by Advanced Nutrients Medical, you can avoid headaches such as the ones you’re having now. Do some research into how much Nitrogen your should be feeding your vegging plants. Start at the website of the company that makes the best cannabis specific ferts in the world.

Thank you so much for the input Wes (and everyone else), I really appreciate it. Now that everything is doing MUCH better, let me explain a little about my setup. I am using an Aquamist IV Aeroponics system, and my girls (hopefully) are just over a month old from the day the seeds cracked. The largest is over 7" tall and if I chopped her right now I could get 10 clones. She is topping at every node (I am getting two new shoots at every node and I have since day 1 on every plant). The stems are extremely thick, which may just be a trait of the Big Bud strain. Within 6 hours of lowering the PH and the nutes, they all stopped burning and continued growing. They are dark, full, and beautiful.

Being that this is my first Hydro/Aero grow ever, it has taken me some time to get used to it, but I think I am on the right track...

Anyway;

The fert I am using is called "Fox Farm Grow Big" and you can fin it here;

http://ecogardensupply.com/xcart/product.php?productid=16441&cat=0&page=1

I suspect when they get bigger that more will be needed, but right now they are simply unfolding before my eyes... Why fight it? But it is designed for compact growth and it is very powerful stuff.

I am using a PH up/down that is made for spas, and you are correct; a few granules will lower my whole system .5 easily. You guys are very correct in that I was mixing and dumping without letting it stabilize... That will not happen again.

Thank you all for your help. I have said it for years... Stoners are the best people

PS - I will take new pics soon.