Kiln dried cedar?
Kiln dried pine is all I use now after changing from aspen and not one case of myco, EVER.
Kiln dried pine does not cause anything and cedar is something I would never put under my rats, just really bad advise....
Masking the ammonia with anything is not healthy for the rat, you may not be smelling it but the rats are still breathing it.
"Occasional small amounts of porphyrin are normal, but large, regular amounts indicate an underlying problem."
There is no way you can go 2-3 weeks with any type of bedding without having absolutely disgusting bedding the rats are laying on, that's just gross.