Looks like Brooklynella. You need to get them out and into a hospital tank ASAP - it's a very fast acting disease, as in you might have 48hrs, but probably less!
Read this:
BrooklynellaYou can get formalin from anywhere that sells pond stuff - most garden centres, and some lfs will have it in. You need to double check your dosages, and make sure you aerate the water, as it depletes oxygen.
