I have a small colony, 6 females and two males. They are all paired up in tubs. They all have roughly the same set up: Stall dry, aspen, water bottle, food hopper.

But the one that i just cant figure out is the only tub with a wheel. I have two small females, one is black, the other, grey back white body. And they SMELL! None of my other rats smell as bad, is this normal? It's not an ammonia smell, or feces, its.... stale? I can't figure it out. It just smells strongly compared to the rest of the tubs. Is it the wheel? Are they just working out more and getting gym sweat? lol. I just dont get it. Help please