One of my ADFs lost a front leg last year. It wasn't caught in the filter, it didn't injure itself in the tank. It just disappeared,no sound or obvious sign of Injury. It managed fine with 3 limbs, but 3 weeks ago, I noticed the web of his remaining front leg had gone. Now his whole front leg has vanished. I am at a loss as to how or why? I have treated him with methylene blue,just as a precaution. Can anyone she'd any light as to why this happened? My other 3frogs are fine...