My wife planted knockout roses several years ago and they were beautiful for several years, but now when in full bloom it looks like 2 types of roses are visible. One is the typical knockout rose, but the other is a ugly small red flower. Is the cross breeding coming out of the bush?
It sounds like your knock out rosebushes were grafted rosebushes. At some point the hardy root stock that the top part was grafter onto got over zealous and decided to send out shoots to grow. It is best to prune out these shoots all the way down to the ground and maybe even a couple inches below ground. Then watch for the shoots coming back, usually the foliage and growth characteristics will be noticeably different, prune them out as they are discovered. Otherwise they will sap strength from the actual Knock Out rosebushes and could lead to their death, preceded by poor performance.