ur not using any nuts or are u still using the veg nuts ? it could be magnesim deficency try putting some epson salts in a foiliar spray should clear it up it worked for me then i got lots of salt build up on the lower leaves tho
Thats ur problem the lights are way to close and with all that heat coming off the lights... try keeping ur lights 3-4 inches from the top of ur plants. that should help