My rat is sick

Question
We recently adopted two rats, Phoebe and Delilah, from a pet store that rescues animals. The two rats got along great with each other so we decided to put them both in the same cage. At the beginning of November we noticed that  Phoebe's back right leg was swollen and she was limping, we all thought that she either got it stuck between the bars of her cage or got into a fight with Delilah. My mom contacted some people for advice and received information on how to treat her foot. She was told to feed Phoebe childrens motrin to help with the swelling. After probably a week and a half we started to see less swelling and she was able to move around much easier. Now just recently she has seemed to have lost a tremendous amount of weight and you can feel her ribs and hip bones stick out, her hair seems to be not as full and she is making a grunting sound when she breathes like it is hard for her to breathe. We have seperated the two rats to try and feed Phoebe more food without having Delilah eat it all but she still doesn't seem to be getting better. She eats, what seems to be regularly, but is still weak and having trouble breathing. Does this have any relation to her foot injury? Do you suggest any treatment? I feel that she won't be living much longer and I feel as if this could have been prevented had we gone to a vet. Please help, I love this rat dearly and would hate to lose her.  

Answer
this has nothing to do with her foot, although she does need a vet or I am afraid you will indeed lose her and she will suffer from the inability to breathe.  She probably has pneumonia or chronic mycoplasmosis.  If treated early, the rat can recover but chance of relapse is high if not treated right.  Also, the vet will need to keep her on medication for the rest of her life because she probably has lung scarring from having this for a while. The weight loss is typical with heart and lung disease.   She needs a vet right away. Her survival depends on it.