I was afraid of epiphysitis with my foal and tried to research it a bit (even did a post on here) although I don't think he has it....yet anyway.
But basically the bones grow faster than the tendons can, so they contract.
It seems like the main treatment is to limit the intake of rich feed, so the growth slows and the tendons can catch up with the bones. So bermuda is a good thing. I don't know about the junior feed. I would probably either cut that out completely or just give very, very little. But hey, I'm not the vet, so I would go by his or her recommendations over mine!
But, it wouldn't hurt to put "epiphysitis" or "physitis horses" in Google, because it will give you lots of information.
Physitis is actually inflamation of the growth plates, but contraction seems to go hand-in-hand with it.