So my White's Dumpy tree frog has become sick. It's been sick for about one or two weeks now. We've had it for several months and this is the first thing the frog has gotten any sort of illness that isn't natural for a frog.
Symptoms include:
-Refusal to eat
-Refusal to move (it has a hard time moving, although it moves fine in the water and kicks energetically.)
-Today we found out it has a sort of red splotch under its back leg.

Now that I've done research, I'm almost certain it's red leg syndrome, as all the symptoms apply perfectly. Although I did notice there wasn't any bloating and the red splotch is kind of hard to see, unlike other pictures I've seen. It looks more like a reddish-brown stain on its back underleg.

If it IS red leg syndrome, what do you suppose I do? What are all the things I can do to help and what do you think would be the best option?

Is there any other possibilities of what my frog might have?

Thanks!