fringes curling up

hey guys one of my plants is 23 days old and has had no nutes yet but the fringes are curling up and i was told it was either nutelockout or heat stress, so i flushd and moved the lights back with no luck. i'm growing in mg (bad noobie i know!) with 2 40 watt t12s in 5 gallon pots watering with aired out tap water tested before each watering ata ph of 6.5. the temp in the room is 72-75 might push 76 on a hot day. this is my largest bushiest fastest growing plant, there is no discoleration. could she need to be re-poted or could lak of nutes cause this(probably dumb question)??? sry pics are a bit fuzzy.... thanks guys!!!! btw 1st two pics are the leaves in question while the last two are other plants with no problems, bout 5 days old though.

please. any ideas??

so i flushed a second time and there was no response, then i started on nutes and once again nothing happened..... but now the plant next to it it having the same problem only on the leaves closest to the origional plant??? it's like it's contagious. both plants are still growing fine any ideas or suggestions???

I had that problem i don't know if leaves curling upwards like that is always caused by the same thing but with me it was lack of nutrients.