Uncle Jimmy

Just wandering if you know much about DWC , im helping a friend who's plants are doing great but all of a sudden three started to dry up, just the leaves. what i've found its either over or under feed or heat stress but all are feed the same and same light. 4 x 400 w lights. they are three weeks away from harvest. any idea's ?

sup man yea im in the new england area if you have any questions hit me up any time i like helping people out and learning at the same time good luck!