If the smell is absolutely awful, try looking to find what their poos like. I know you said it may not be pee or pee, but it never hurts to check. If they're firm and have a shape, then they're healthy. If they're greenish, squishy, and absolutely smell, it's diarrhea. Too many "junk foods" (things like treats, which is what I use in moderation for trust building) and fruits cause serious diarrhea. Try giving them whole grain cereal such as Cheerios or corn flakes to firm their poos up. Vegetables high in fiber can help harden poos as well.
If they, the rats, smell absolutely horrible, try bathing them with unscented, baby shampoo. I use Johnson and Johnson's unscented baby shampoo. Never had a problem with any of my male, unaltered rats. And they even smell kinda good (even though my shampoo isn't scented). Also, check their genitals, see if there's any urine or fecal matter build-up.
As mentioned before, I'd be careful about cleaning their cage every single day. That's too often and too stressful, in my opinion. My huge DCN gets cleaned once a week, and the rats are bathed the same day. Deep cleaned with Dawn dish soap once a month.
Any cardboard or wooden hides may smell as well, especially if the female rats urinate on them. I usually give cardboard boxes a week in my rat cage, maybe two if it's in really good condition.
I don't recommend putting rats in an airy room, but don't be afraid to get the fan going to keep air circulating. Sometimes stagnant air is the worst enemy with rats, especially if the cage is a little closed off. That's why fish tanks make terrible cages for rats.
Good luck and I hope you get it sorted out!