I've got two Cornuta from mike same size as yours. They feed well. I do have to tap and rub my green on the mouth a little, but the other will take what I am feeding without touching.

Just be persistent and they will take it. Mine will only eat every third day...I'm used to my pyxies. They eat everything in site no matter what.

None of my Pacs will eat red wigglers. I think they smell different prey which is strange as hell to me. I didn't think they'd have a very good sense of smell. This might sound goofy to say they smell really well but there is no other explanation for why they will take some food willingly and other food grudgingly, and some not at all.