Swollen legs... immune problem? rash? lots of problems...?

Okay so my thoroughbred, sid has more problems. We called the vet out again (third time in two weeks) and had him look at a strange rash that looks like scratches (the fungus) on his nose. The vet said it could possibly be something else. He checked him all over and noticed that three of his legs were slightly swollen. Not swollen like big, but just slightly. It was only on the legs that he has white socks, and the swelling was from the knee down. Once again it wasn't thick swelling, just enough to where you can't feel his tendons.... please, any advice would help. Thanks