can anyone offer any idea what this can be.

[tallslim]

has this happen to anyone while growing.

 

[Mutt]

Can you take a pic of the whole plant? also answer the questions you can at the link in my signiture "help us help you".

 

[Hick]

My first thought was magnesium defficient. (interveinal chlorosis) Usually in combination with 'cupping', 'canoeing', or 'praying' leaves, reaching for the light, though.

Miracle Grow?...

 

[skunk]

i had a couple of leaves that were yellow like that but it was where most of the light was concentrating at . but it also looks like you not only have cupping looks like a leaf in the back is drooping . if it were me i would just flush the hell out of it with water and check on it tommorow .