From what I saw of that frog when you first got it there was no disease. It is highly likely it was born that way. I have seen several with deformities including deformed and extra linbs. That's what happens when us humans are hell bent of saving them all. lol
A store can have a good reputation and still unknowingly get diseased animals in. Chytrid is tricky and took a while to detect and learn how to treat it.
Here is a site with treatments. To my knowledge the only method that works is the Lamisil treatment. I would not waste my time with the other BS.
Chytrid Fungus Facts and Treatments