I have some Paramesotriton sp. that when I first got them developed swollen lips and grey patches on their bodies. I was keeping them in a bare bottom tank and making frequent water changes with no improvement. In fact they started to get worse and stopped eating. It got to a point when I thought they weren't going to make it. So I tried a last resort treatment using a product called Melafix by Aq'm Pharm., a remedy I had success using in my fish aquariums, made from Melaleuca ( a "natural" antibacterial agent made from the melaleuca tree, I think). Within two days the newts started to eat again and within a week the grey patches had almost totally disappeared. Only 10 days later the infection was apparently gone. Now it would be irresponsible to say that this product was a cure all, and this one case could be pure chance. But I mention it if things get worse with your newt, you might want to try it.
I am curious if anyone else has tried this product on their newts? One of the reasons I did try it was it's claims that it wouldn't even hurt invertebrates in an aquarium. I figured if it wouldn't hurt a shrimp it couldn't make my newts worse. My Paramesotritons have done extremely well since that point in time and have had no reccurrence of the infection.