Eeeesh!! I've never seriously attempted to breed neons, or feed them enough to condition them for breeding, so I'm no expert... but that just doesn't look right to me.
If that were mine, at very least I'd isolate it in a breeder box (along with some plant trimmings to help ease stress). And fast it for three days to help with any potential digestive issue. Should it die as a result of some infection, it will be easy to locate and quickly remove; and the other fish won't be able to nibble on it in the meantime, which could potentially result in more infected fish.
If I wanted to maximize chances of survival, I'd remove it to a separate quarantine tank. Water at 78°F, treated with Epsom salt and Kanamycin. Fast for a couple days, then a couple days more of feeding shelled/blanched peas (if it will eat them).