PLEASE HELP! eggshell coloured leaves!

my plants are still in vegging and the lower leaves, starting from 1st node are starting to turn an eggshell colour and just flaking off, its been happening for about 2 weeks and one set has just died in my best plant.
What is the problem?

Any help appreciated

check this out, see if your leaves fit one of the descriptions.

International Cannagraphic Magazine Forums - The Complete guide to Sick Plants,pH, and Pest troubles!

thanks alot, i've flushed the plants for nute burn, and i'm moving the lights away because of heat stress. i'll wait 3 weeks before adding fert at 1/4 strength.