loss of weight, and nasal discharge+sneezing

Question
I have three male rats, I make sure I clean their habitat once a week, and use the recycled paper bedding.  two of my rats have seemed to of lost weight, the one ratty constantly makes a grumbling sound, that I suppose is just teeth grinding, my other rat scratchy, has nasal discharge as does ratty and they both tend to sneeze a lot with clear nasal discharge.  I am not sure if it's a sinus infection or not, as both posture seems quite normal, they also don't seem to be eating as much as they use too.  My last rat shake is fine.  I am wondering what exactly could be wrong, and if they have a cold, what I could give to them to help fight it.  As for going to a vet, it's a bit costly where I am, I live in Norristown PA, and can't afford much, so any help with anything would be greatly appreciated, thank you.

Answer
Hi

First of all, please read up about mycoplasmosis in rats.  Let me know if this sounds like what your rats are going through.
Get back to me right after so we can continue our "virtual exam"  :)

http://www.freewebs.com/crittercity/mycoplasmosispage.htm