Nute Problem? Am I playing it too conservative?

I started 9 CH-9 Jack Fems from seeds in rockwool about 2 weeks ago. 2 days ago I noticed some yellowing on the tips of one of my seedlings. Another one is now showing some faded spots and now its tips are yellowing too. I'm concerned b/c I don't want to lose my first hydro-crop before it even enters veg.

I feel that I've been conservative on the nutes, as I heard burning is a common newbie problem. Heat is also an issue, so I figured lower on the nutes would be better. I was using 1/2 the recommended strength 3-part GH Flora Series for seedlings until today (Micro:Bloom:Flora 1/8th tsp / gal distilled h20), then fearing I had N deficency I upped the strenght to just under the GH recomendations (1/4 tsp / gal distilled h20) when I transplanted them (in the rockwool cubes) from the garden flats to the GH Rainforest today.

Here are my notes and some pics:

Space: 2x4x7 tent
Vent: air exchange via 2 160cfm inline fans run 15m/hour. Internal circ 24/7 from ossc. clip on fan.
Light: 600W MH Conversion Growbright lamp (claims 72,000 lumes), 20x24" Aeroflow Reflector (inline fan cooled). 26" above plants.
Planters: GH Rainforest 66 Aeroponics run 1hr on 1hr off 24/7
Air Temp: 80-93F (26.7-33.8C) (I'm working on cooling it down)
Ph: 6.0
Nutrients:GH Flora, 1/4tsp / gal. TDS=approx 150ppm, but "dirty" hydroton and Hydroguard I beleive accounting for much of that. GH calculator puts nutrients at 75ppm.

I'm thinking N deficency is the problem, but other suspects include: high temp, overwatering (before transplant, while in the flats), too much light, too little light, global warming, and Joe the Plumber.

Any ideas?

Looks like nute burn, little ones like that dont need any nutes.

are you adjusting your nutes solution ph after adding the nutes?i start mine out running around 300 ppm,using the lucas formula.gh products.micro and bloom only.

My ph is 6.0 after adding my nutes. I think I'll continue running at 75ppm for a few days and see if the leaves look better / worse then switch to Lucas (300ppm, no floragrow)

a little high on the ph i think.i like to keep mine at 5.5-5.8

InuYasha said:

My ph is 6.0 after adding my nutes. I think I'll continue running at 75ppm for a few days and see if the leaves look better / worse then switch to Lucas (300ppm, no floragrow)

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I would, keep an eye on the new growth tips if they stay burn free up it to 300.
the burnt tips you have now wont clear up.

6.0 is to high for hydro. I start my seedlings out at about 300 ppm after they root through the bottom of a 1" rockwool cube.

I start adding nutes to my seedlings when the cotyledon (first, rounded leaf on a seed grown plant) starts to turn yellow. That usually happens about the third week after sprouting. With clones, when I see new growth on the top of the plant I start out with a weak nute solution.

Peace...j.b.

Thanks again for the advice.

The new growth looks good and yellow-free.

I will lower my Ph and try upping my nutes slowly to 300ppm over the next few days. I am also going to try lowering my lights (from 26" to say 22"?) now that I have a new fan and my temps have dropped to about 84F 'under the sun' and about 80F shaded. Hopefully, once this fetid swamp realizes that it's winter, the temp will drop to the mid 70's.

When can I start saying that I've entered the veg phase?

I increased my nutes to a modified half-strength Lucas formula. 2.5M-5B-1.14G. According to the calculator on CannaStats http://www.angelfire.com/cantina/fourtwenty/articles/profiles.htm My PPMs are as follows:
N=40
P=41
K=62
Mg=28
Ca=36
Total 207

My TDS meter still tells me I'm at 270, but I think that's because of some contamination from my 'dirty' hydroton and some hydroguard I had added.