How Do I Get My Pet Rats To Eat?

 
How Do I Get My Pet Rats To Eat?
I had 3 pet rats but sadly one of them died on sunday. I am now worried as the other two are not eating well. I know They may be grieving but I am worried. They will eat bread and raisins and treats but they cannot live on that and they hardly touch the regular food when in the past it would all be gone within the hour. These are my first rats. Is this a phase that will pass or will it take a lot of pursuasion. Please help as I am so worried. Many thanks. Alice