So I don't have a camera capable of taking a decent picture, but I'll try to describe the algae I'm seeing as best I can.
It's only occurring in my rotalas after I trimmed them and replanted the tops. If this is what the growth tip looks like, \ / , the algae is a dark green spot nestled right where new leaves should be coming from. Looks like this \o/, where the o is a little spot of algae. It's only right at the growth tip, on none of the older leaves.
Anybody have an idea what this could be and how I can treat it?
Well thank you for giving me an idea of what it could be. It's also good to know that it went away on its own in your situation. I'll probably ride it out and see what happens... I just hope it doesn't kill the stems because I replanted the tops and didn't save any of the bottoms :/