1 plant never happy

Sweet answers guys thank you!

And run a few 3-4ltrs of plain water through it just before your next feed.

Seaweed is great for many issues.I use Algen Extract from House and Garden,its Norwegian Kelp.Its one of the few things where you can see the impact on the plant straight away.I see you've also been told to use Microbes.I also use Biosys from Ecothrive,its an instant Compost Tea,its got Microbes,seaweed,humic acid,amino acid,enzymes and molasses in it.Its more effective if you bubble it with air but it can be added straight to half strength feed.I can't recommend it enough.Iv not had a problem with seedling damping off with root rot or mildew and mold in buds in the 10yrs Iv been using microbes.

This a nitrogen deficiency or lockout, you can because the older, lower leaves on your plant to turn yellow, wilt away, and eventually die. The plant typically appears pale or lime-colored, just like yours.