Help:DWC grow>> Sides of the leaves turning upward on just 1 of 3 AK 48's

Need some help, please. I have 3 femmed AK 48's from seed vegging in a DWC. They are 3+ weeks old 6-8" tall and on AN 3 part nutes w 1/4 tsp per gal of Epsom Salt for x-tra mag. Ph is 6 and ppm's are 850 ish. Water temps are cool and they ar under a little 250w mh... They all look very green and bushy and have lots of white healthy roots but, the sides of the leaves on just 1 of the 3 plants are turning up. Please lmk what you think is the prob......thx HGH

pictures please!

no pix now....leaves green and healthy except 1 of the 3 plants has leaves that are cupping/curling up on the sides but green. .maybe it needs more air. I'm gonna move the fan a bit to give it more air.