weight loss in rat

Question
QUESTION: Hi, I'm from the UK. I have 3 pet rats. One of them seems to have lost quite a lot of weight. They all used to be around the same, quite plump, but I can now feel her spine a lot more and she is noticeably lighter and visibly thinner than the other two.
I've also noticed over the past week that her sight has possibly deteriorated. She is using her nose an awful lot more and doesn't seem to notice treats or anything unless you put it right up close to her face. She is grooming normally and snatches treats and food out of my hand and hides it away as normal. She is about a year an a half, same age as the other two. Bedding is shredded newspaper. She has never has any previous health issues. Let out to explore regularly and very much loved. Oh, I have also felt her stomach, and cannot feel any masses and she doesn't squeak when I do this, she has no red discharge around eyes or nose, although she has had this before.
The other two rats seem to pick on her a bit recently. They are normally a happy little unit, playing and a bit of rough and tumble, but recently they seem to bully her a little bit and the playing gets out of hand, although I cant see who starts it. I suspect the others are playing and if she has indeed lost her sight, she might be striking out against them. I'm not sure what to do, or if there is anything I can do. Apologies if this is a bit long winded and doesn't make a lot of sense!!
Please let me know if there is any other information you need, I'm just looking for advice really, wondering if you have experienced anything similar.

ANSWER: Hi there

What type of diet are the rats eating and do you keep food down at all times for the rats to eat whenever they want to?

Also, do you notice any heavy breathing or do her sides seem to cave in when she breathes?

---------- FOLLOW-UP ----------

QUESTION: They eat nuggets and mixed grain  bags of food from the pet shop and i give them bits of fruit and cereal sometimes. Oh and i buy those treat sticks of grain and dried corn cobs from the pet shop too. They have a constant supply of food and water in their cage. her breathing seems normal, apart from her using her nose a lot when out exploring and her sides don't cave in.

Answer
It would not be a bad idea to look into changing the rats diet to lower protein and fats. The corn cobs your buying are not the best thing to feed your rat, either. Hard dried corn contains
has been found to contain high levels of fungal contaminate.  Rats fed this corn, including the same hard kernel corn found in rat mixes sold to the public are much more prone to liver cancer.


Please check out my website for more info on proper nutrition.

http://www.sandyscrittercity.com/ratsandahealthydiet.htm