Hybrid Syndontis catfish extreme aggression?

I have a large 8-9" Synodntis hybrid in my tank that has never bothered any of my fish but I have a 5-6" individual of the same species that has started showing extreme aggression towards many of the fish in my tank. Even at the moment he is fighting (coming up beside and barbing in the side) with an equally sized Syno decorus and has seemed to have been getting worse all the time. A few weeks ago I noticed one morning my 14" BGK was a bit beat up one morning when i turned the lights on, he had a few white cuts on his side and his fins were very tattered. I initially blamed this on some of my young vieja cichlids but I witnessed a long and scary fight between the knife and this catfish the other night that must have been the cause and it seems like a daily thing now. Anyone else have this issue?

Also to be added the fish in question never attacks the larger one of the same species.