Alright, without seeing that last pic I'll give you my best guess. I've never had personal experience with this, but going but what I know and have read, I'd say fish pox is a possibility. It is a caused by a viral infection and shows up with these growths. According to my book, "fish pox often appears, develops to a certain extent, and then subsides and disappears, sometimes to reappear at a later date. It is not very infectious and other fish in the same tank may remain unaffected. It rarely causes any fish losses." There isn't a good treatment for it, though raising the water temp quite a bit can eliminate it for a short time. Overall, as the book again says, "it is unsightly rather then dangerous". So you're lucky if that's the case!!
I'm assuming they're acting fine besides this?