Is My Rat Dying!? Please Help?!?

I Adopted a rat who was 12 months old at the time. it was love at first sight. she is now about 17 months old, names bubba. i also bort 2 more baby rats who have been living with her ever since in a happy environment. 3 days ago i found alot of scabs on her back and neck which were bloody. i thought she just had a fight. today shes hardly moved in her large cage, and one of her eyes seem to be slightly enlarged and very , i have moved her away now to a seperate slightly smaller cage giving her everything she needs, i cant afford the vet bills but im trying to search what could be wrong. she seemed very lathargic. i have placed her in a new cage seperate from the others (who are both very very happy and healthy) and she seems to have perked up abit but i dont no what to do?! usually she bites but when i went to pick her up she didnt attack me atall. maybe she wanted my help. i have been sittin here with her on my lap just stroking her and she is now sleeping i just want her to go peacefully and be compfortable coz the other 2 rats are only about 5 months old and very energetic. please help