Treating Cats With Dry Flaky Skin?

My (2) 13 and 9 year old cats fur are have started getting mats and when I comb them out, it looks like they have dandruff too. What could be causing this? I only feed them a very good brand of dry cat food. Could something be lacking in their diet?

Any suggestions would be greatly appreciated, as the 9 year old does not like to be combed.

By CHERRIE from Rock Island, IL