For the last two months or so this darker shade of green has been growing on some of my anubia leaves. At first I thought maybe it was a deficiency, but it seems to be spreading in a fashion that I think it might be something on the leaf itself. It's a 10 gallon betta tank with maybe 60 shrimp in it. I fertilize every few days with a squirt of aquarium co op easy green and a capful of seachem flourish.

Deficiency or algae?