I would definitely start changing the paper towels daily instead of weekly. Also, you're probably already doing this, but change out the water dish in addition to its once a day change if you see it has any waste in it (my boys seem to think fresh water is the best for pooping in, so I sometimes have to change it twenty minutes after I just did). With red leg it is important to be hyper vigilant about keeping the enclosure clean.

I'd also recommend bringing him to see a vet. Choose the one with the best reviews (very few ever have entirely perfect reviews) and that you know has herp experience. You might even be able to talk to the vet over the phone to ask a few questions and confirm they know about frogs before making the appointment (depends on the vet).