help! What is happening to my frog spawn?

[Coasting]

If you can simply break off that left head thats totally jelly-ized do so, otherwise pull the thing out, grab a new toothbrush and scrub out all the dead brown tissue. Then gently if you can in a little cup of tank water, clean around the edges of the one thats still green.
The brown jelly will continue to spread if its there, but sometimes if you get rid of the nasty part, the part thats still somewhat alive may still be able to be saved.
When youre done put it in a low flow lower light spot away from other coral to see how it does.