my rat has gotten thin and dizzy

Question
hello,
 i adopted 3 female rats temporarily from my sister and really have grown attached to them quickly.  my question concerns the eldest of the three named roxy.  this week i noticed roxy has been losing weight and i gave it a few days and today i noticed she was having problems navigating around the room.  she isn't completely stumbling over but i paid special attention today and it shocked me to see her tip over a few times and be generally slower and not sprinting around after i let her out.  there definetly is a problem i just have no idea what i can do about it and it bothers me alot.  i have not taken any of them in to see a vet because of the sheer expense but that doesn't mean i won't if it is what i need to do to stabilize her.  i feel helpless right now and hope you can give me some advice.  i feed them all good quality rat food and grapes for treats.  they all get 40 minutes out everyday to run around and crawl on me.  i hate to see roxy under diress....

sincerely,

dylan

Answer
She very well could have an inner ear infection which is treated super easy with antibiotics and something from inflammation.  The pressure from the inner ear will cause her to be off balance.  Let me know something:  is she able to use her front paws to grasp food etc...?