Rat scratching excessively

Question
Hi Sandra,
I wanted to ask your advice about my pet rat Terrence.  He is scratching a lot and every morning I find scabs with tufts of fur on around the cage.  I think this might be related to his diet from what I have found out on the internet.  I feed him Pets at Home rat nuggets which are supposedly quite balanced.  I also feed both my rats a small bowl of fresh food every day & some oats or other cereal.  Terrence always goes back in the cage early at playtime so he can get to the fresh food bowl before my other rat Noel.  This means he always gets a bit more than Noel.  As Noel doesn't have the same skin problems I'm wondering if it's something in the fresh food that's causing the skin problem for Terrence.  I used to put a lot of peas & some fresh sweetcorn in the food bowl but have cut this out now as thought it might be too much protein.  Now I put a small amount of rice noodles, some brown rice, brocolli, carrot & pear/grape into the bowl.  Do you think this is ok?  I have also cut right down on the oats.  At the moment terrence is still scratching but I have only changed the diet for the last 6 days so maybe this is not long enough to make a difference yet.
Any advice you could offer would be much appreciated.
Many thanks,
Suzy

Answer
How much protein are in the nuggets?  
Its best to keep his diet at or around 15% or so.
You can give him peas and a bit of corn, the protein is low in both veggies. Have you taken a magnifying glass to him to see if you see any critters moving on his skin?