Could this be a yeast infection in my son?

I have a 15 week old, and his area smelled bad today I noticed before we gave him a bath, more then it usually would. And it looks kinda red and splotchy down there aswell. hes had a case of thrush that we finally got to go away (we think) so I was wondering if maybe its a yeast infection down there now? My husband swear its because hes uncirsized, is that whats causing the foulness?