Good idea ,put them under a cfl to recover.I too recently tried hydro... love it. And I did use any nutes until the colydon (spelling) leaves died off. Then I started to feed at 300 ppm and worked up from there, keeping pH under 6 and no lower than 5.3. I also found that starting them under my T5's was better than LEDs to start.
The pH dropped a couple times to 4.5 but I have been using pH up to keep it at 6-6.2 I'm using pure blend pro botanicare nutes.400 hps lights 20 inches above the plant only the one has an issue the rest are beautiful. The amount of nutes is currently 225mg to 20gal of water this is the beginning of the second week of veg.Boron deficiency? No chance.
What are you doing for nutes and feed levels? Ph?