It sounds like your cats may have picked up a mild case of rhinotracheitis, an upper respiratory problem that might be compared to a cold, although cats do not get colds in the way we do.
If your cats are indoor and healthy, it should pass in a week or 10 days. Just be on the lookout for green discharge from eyes or nose, or any wheezing. This would indicate a secondary infection and a vet visit would be necessary.
Make sure they are eating and drinking too.
My own 3 cats just had a little case of this just recently, with sneezing only, and now everyone is fine.
MBRA518 - your cats had feline parvo?? This is a very serious disease and requires treatment.