Crypt dying back?

[Seized]

I have a crypt wentii red in my 20 gallon community tank and it was thriving for about ten months but its been dying back for about a month now. Not sure if its a nutrients problem but i dose easy green weekly and the gravel is very full of mulm. It also has a small GSA problem but i dont think thats the problem. Please help.

 

[Jessica.]

Crypts are heavy root feeders. You probably need to add some root tabs. I know you said lots of mulm is there, but hearing they did well for 10 months then slowed sounds like the depleted the available nutrients in the substrate.

Edit to add- assuming nothing else has changed in the tank, like if you changed your light, or increased the temp, or bought a fish that's started eating it.

Edited November 1, 2020 by Jessica.