Colony of feeder rats that are optimaly cared for! But seem sick

They can spread viruses and parasites through contact and feces.

If you have a wild mouse problem, they will leave signs. Check the surfaces, around the base of walls and shelves.

Old fashioned spring traps are the easiest to use. Bait with peanut butter. I use a suitably sized old food container with a hole cut in the side to put the trap in. Keeps the dogs from getting their noses hurt. Also, I think the mice are actually attracted to the small spaces inside.

What are you using for bedding? I was throwing out 1-2 dead rats per day from my colony when I was using very dusty pine bedding from the feed store. Pine bedding is very toxic to rats and can kill them! Especially if it's really dusty. I changed to a shredded paper and newspaper bedding and have only lost one rat in the last month, and I think he died from old age LOL.