I've seen marks like that from plecos and from other rays (but more often from other males rays as they become mature). I'd remove one and see if it gets worse- if it still does try the other one!
looks like male maturity aggression bites, I'm not sure about pleco bites because I don't house any pleco.
the area where he is bit-up looks like where my male will bit the female during breeding, he did this as well to my male orbignyi after I sepperated him from the female.
looks like male maturity aggression bites, I'm not sure about pleco bites because I don't house any pleco.
the area where he is bit-up looks like where my male will bit the female during breeding, he did this as well to my male orbignyi after I sepperated him from the female.
Pleco or fungi... remove pleco & salt. Generally ray bites are around the disc where the other ray gets a chance to grab a quick bite. If you have rays that are getting bit on the top from other rays it means the ray is ill & won't move out of the way... not good...