Rats that either came from a pet store or rescue often do have 'sensitive' resp issues throughout their lives. I am not saying they all do but inbreeding and woodshaving/sawdust/tanks all aggravate a rats delicate resp system, I know you do not keep your rats in such conditons but its highly likely where ever the rats where born was like that since well bred rats would be returned to their breeder, not a rescue.
It is also somewhat normal for them to have porphyrin (red staining) on their eyes/noses just after waking, a bit like 'sleep' in other animals. However this should be the tinyest amount and they should clean it up right away.
You sound like you are doing a grand job anyhow, if your still worried or other symptoms develop visit the vets
It is also somewhat normal for them to have porphyrin (red staining) on their eyes/noses just after waking, a bit like 'sleep' in other animals. However this should be the tinyest amount and they should clean it up right away.
You sound like you are doing a grand job anyhow, if your still worried or other symptoms develop visit the vets