Two things, you need like 4-8X as many plants and the tank's CO2 was terrible not too long ago, but some decent growth from the stem plants in recent times suggest you may have done some much needed work on the tank there.

Those leaves cannot be saved, even if the algae came off, they look ratty.
May as well export the algae that's there, buy a lot more plants etc.

Regards,
Tom Barr