Guppy missing an eye?

[Szibbs]

Hi, I was watching my fish swim around for a few minutes then noticed my lyretail guppy was missing an eye. When I got him he had both and I don't know what happened. He seems fine, there's no blood or any signs of fighting. Is something wrong with him or will he be okay?? I have a 3.5 gallon tank with the lyretail, a cobra guppy, and a fancy guppy. They are all males and seem to be friendly with each other.