Need more info, but if your feeding proper then I'd look at soil pH. Have you flushed them at all during their life? May be too late but may be the the cause of a root zone problem, if that is the case.
This looks like it could be a combination of things. It could be being burned by the light. I'm not convinced it's a root zone problem. Leaves seem to be expanding, there's no indication of micronutrient problems, which you'd see when the pH is off.
Note the lower leaves don't have as many issues — just some leaf tip burn. How close are the tops to the light?