Dart Den

I have a wild caught orange mantella over 5 years now, probably more. the problem is the last few days he I think its he was seizing. I have put him in a qt tank with sphagnum and a few leaves. I didn't see any red leg disease. but he is bloated or at least looks bloated. as far as supplements I don't do that as much I as should. feeding flies and pinhead crickets. by my description any one might have an idea what it could be. I know it is vague. would try to treat it but not sure of what to get.
thanks for any info.