There wasn't any blood anywhere else in the tub. As I said in the original post he was last examined 36 hours prior to the discovery of the injury and looked fine at that time so I don't think a eye infection could have progressed that quickly to the result pictured above (although I'm not 100% sure, I'm not a vet).

I examined the tub area to make sure there were no sharp points sticking out anywhere but didn't see anything. My best guess is the eye was injured somehow during their play fighting. I've just never seen this kind of injury as a result.