cupping, drying crispy leaves

so this is my secong post my other plants are doing good ive got off the nutes and built a water resevior with a bubbler in it and the plants are about 8 inches high and just a bush but my veg room is where im having my problems. im on a very consistent water program i was having bad luck with nutes so ive been flushing with water for about a week now and my leaves at the top of the plant are cupping and turning brown and crusty kinda like they are burnt but my light is a foot above them and im using a 400mh with sunmaster bulb. im thinking its the plant because the other plants i have in the same room are doing fine. these plants have been fairly tempermental since the beggining but oh well please help heres a picGetAttachment.aspx.jpg
 
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