leg problems rooster

I have 2 roosters, different breeds, different pens, about 2 weeks ago they both started having problems with their legs. It was right after we had alot of rain and mud in their pens. They are eating, drinking, no nasal discharge, no other problems, except they spin in circles and seem to have a problem standing for a long time.

They can stand and walk, but sometimes the opington will be on his hocks. any ideas on what this could be.