I fought something that sounds similar to what your going through. My African Cichlid's were getting open sores, ulcers and bleeding. There mouths were getting white and there body's looked like it was being eaten from the inside!
I lost 15 Cichlids to this disease I now know is called columnaris. It's horrible. What I did was lower my temp to 70-72 degrees and used kosher salt 2x's a day. Once in the morning and once at night. My plants didn't like it but I dosed the heck outta my tank with kosher salt. I forget how many tablespoons each dose was but I'd say on a 15 ounce cup it was probably a quarter full. I mixed it with water and put it in the tank in a high flow area. It took some time but after a few weeks and 15 fish I beat it. I have a whole thread on it. I'm not sure if columnaris just effects Africans but you may wanna look it up.
Oh I almost forgot. I also dosed a med from the LFS
crazy expensive I had to do a double dose and NO water changes. I had to remove any and all carbon and just let the tank saturate with salt and meds. It worked though. The medication was Maracyn 2 and then when I consulted the company and a vet after the first round I went with Maracyn Plus. All those meds and the kosher salt everyday followed my the lower temps killed the bacteria. Everything is good now an I even ended up with two yellow labs holding.
It took ever ounce of myself not to give up! I was losing 3-4 fish a week!!
Heres a good read. And I hope it's not it.