This is often caused by Costia, which is a parasite, or perhaps by some trauma to the skin. I'd salt bath these fish as first line attack and if it was necessary then I would administer an anti-biotic injection.

Breeding-activity can also cause raised scales or perhaps parasites have broken the skin and bacteria are starting to infect the areas. Costia infections may also cause raised areas of scales but a microscopic examination would be required to definitively prove that. 

Instead, you can establish water quality by careful testing and if all that's normal, you'd be wise to salt bath the fish according to our previous instructions - and this would be probably the first thing that I personally would do.