OG Kush leaves turning upward???

alright...trying to do my second grow at this time...hydro-ebb and flow with 9 plants (5 different strains) and using canna products with 600 HPS light...the only problem i am having...while in the veg state, the top leaves of my og kush are like, folding in the middle upward...all the other plants are super looking and dark green...anyone know anything about this or how to fix it?

need more info like, how often watered, how much(ppm, ph), better description needed pics are even better..................

they get watered three times a day while the light is on from 6pm to 12pm the next day...it stays off from 12 to 6...giving it 6 hours of darkness...the ph is under 6.5 but not less than 5.5 and the ppms with my water here in souther cali is like around 800, maybe a little less...the 600watt HPS is like two and half feet from the plants...i will take pics if needed though, hope someone can help me...

might need pics but if they look otherwise healthy and just folding even along the main crease but the tips aren't curling, might not even be a problem. might just be a little streching. ive got a shit load of seeds that are doing that and are otherwise healthy. i dont think it an issue. pics may explain better.

Mine did that the other day.They went back down after a good watering. Maybe they are thirsty? When was the last time you watered them?

too close to lighy and or over nuked

yeah light sounds right ive got my 4 foot 4 bulb t5s 1-2 inches but it doesnt seem to harm them. anyone know?