I'm inclined to say stop using bleach... A little doesn't hurt, but personally, I don't use it at all. I take my buckets down at the first of each month to clean them, and I've never had an issue with any mold or anything else.
And, the Bleach wipes too... I use a product called kennel-sol. Much like the other germicides on the market, designed to kill and clean. I use it once a week and let it soak for a minute, hose it out completely.
And, lastly, someone else hit it on the head... Jumbo/Collossal rats= retired breeders. I sell off my retired males as jumbos but for food only. I start all my colonies off the exact same way. 3 medium females to one medium male. I keep all my holdback females together until they are ready for a male, so that they already know each other. I also replace my males regularly, usually when they get to be a jumbo size, they get replaced. they tend to get lazy when they get older...