Your diary is incomplete and a lot of the information people would use to help determine your problem is not an option.
Its only one week at the 8th week and has no information on what your feeding it, PH, EC anything.
If I had to guess, I would say this might be a lockout issue from either PH or overfeeding it.
Again hard to tell given lack of information, Try adding more details and it should yield you a better answer.
Best Of Luck!
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