Green spots on my brown leaves... but not algea?

[Galager]

My 10 gallon tank is about 4 months old.  I THINK I put in crytocyrn parva (I was a bit overwhelmed and forgot to write down the name of what I got) in my tank along with some other plants.  I have read that c. parva will 'melt away and grow back.  This isn't melting away.  It just has been turning brown but leaving some bright green spots on most of the leaves.  This is only happening with my c. parva.  I don't have a green algae problem (I have a little black algae starting on my s. repens) so I don't think that is it.  These spots don't fit any fresh water plant problems that I have been able to read about.  I add Seachm's Flourish, Flourish Iron, and Flourish Excel in small amounts (about 1ml) twice a week.  My alkalinity is a bit low (around the 40s) as well as the carbonates (around the 40s), otherwise the water is in pretty good shape.

Can anyone give me some clue as to what is causing this because I don't seem to be getting any new growth that doesn't develop the same problem.

Edited May 30, 2021 by Galager

[Sarina]

That definitely looks like green spot algae. It’s notoriously difficult to get off of the surface of anything, including plants. If that is parva, the color is supposed to be a bright green, so it could be that your plants are just melting during conversion and the algae is feeding on the dying plant matter. Crypts usually come back, but making sure you’re feeding the roots is key to helping crypts thrive. 

[Mmiller2001]

GSA is usually present on slower growing plants under too much light. Another cause is low phosphate. 

I would increase P to 1-2ppm and observe for several weeks. If no change, drop light intensity.

 

Edited May 31, 2021 by Mmiller2001