Issues w/ my first hydro grow.

This is my first grow and having issue's with some of my plants. Can't see the pics on my computer in the "grow problems" forum, so am posting here. Growing 4 fem. vanilla kush (Barneys Farm) next to 12 plants started from seeds of regular schwag in a 2x4 flood and drain hydro set-up. (they sat under a T5 light until the serrated fan leaves were showing) the KUSH are sitting on GRODAN BLOCKs and the SCHWAG on 4x4in. GRODAN CUBES. It's lit by a 400w MH cool tube. It's being aerated w/ 4 air stones.

Using GH Flora Nova, Rapid Start and Floralicious Plus in 20 gl. of RO water in a 27 gl container that is under the flood tray. Have it set up to flood for 15m 4x per day. PH ranges from 5.8-6.1 (using a HM Digital PH pen) and PPM is @ 440 (EC of .9). (Its on day 8- just changed the water and nutes but have not flooded yet) and having issues with 3 of the Kush's. 1 is small w/ 2 yellow spots, and 2 have discoloration and wilting. the fourth seems fine (and have attached that pic as well)
all of the schwag plants seem fine and growing strong. (2 or 3 have mild drooping) Have attached pics of the KUSH and hoping for help.

Amatuer theories on issues.
1. started the kush using paper towel technique and waited too long to put them in the mini-Grodan cubes. By the time I put them (after about 6-7 days) in the cubes the root was about 2-3 inches and was quite difficult to put in without having to handle them a bit, (which I now know is not good). the schwag seeds were started right in the cubes.

2. for budget reasons have skimped on cooling/temp control. using the ceiling fan and some small fans at the base of the tray. I live in central TX and the spring has been mild- I leave the windows open (screened) for air flow/cooling. This is probably not adequate so I now have all windows closed and the AC running at 71 degrees F.

3. the nutes are in the middle of recommended range, and have read that the ranges may be on the high end.

would appreciate any help/input. Thanks.

That looks like a lack of N. Does the flora nova have N in it?

I'd have to guess the same thing, N deficiency.

Checked the back of the Flora Nova, and it says 7% Nitrogen (.09% Ammoniacal Nitrogen, 6.1% Nitrate Nitrogen) From a lot of reading I've been doing on International Cannagraphic, I suspect I may have Nute Burn. It recommends using only a 1/4 of what manufacturer suggests regarding the use of chemical ferts. Emptied out the reservoir, and started a new solution w only a quarter of what I used bf. PPM is at 290 and EC at .7. If it were N deficiency how would I address that? Thanks for the quick responses.

I think they have too much water. The rock wool, contrary to popular belief is very easily over watered. By flooding the cubes 4 times a day you are keeping them saturated to the point they are suffocating. Remember plants roots need fresh air too. You gots to let the rockwool dry out before you water again. I bet you could let those plants go for a week nearly in those sized cubes.

kpw555, I'll follow your advice and stop flooding for a few days and see how they react (and afterwards reduce to 3x a day w a much lower ppm). It's been quite a steep learning curve, thanks.