Sick fish, red eye, please help

[Squibs]

Hi there, one of my fish has a red eye and small red bumps on his skin. We changed half of the water recently and have only noticed it since. He seems to be swimming about okay, but I'm worried. We are quite new to caring for fish so any help/advice would be appreciated. I have some pics but can't figure out how to get them on here Thank you xxx