@BynnyRibbit - thank you! Any personal experience is helpful
I'm not sure if they were giving him calcium/D3 before I got him, but I am going to end up making a vet appointment this upcoming week just to get him checked out either way. His mouth isn't droopy like in some of the pictures I've seen of frogs with MBD, which makes me wonder if it may actually be respiratory. Either way, better be safe than sorry!

He was in a smaller container when I got him, so I have a feeling that's what he was fed in, too. I'm giving him a few days without pushing worms in his face, so my next plan is to get some larger crickets + a smaller critter keeper so he feels more secure and testing that out.