I am going through this right now, treated with FishZole and seemed to work at first, then she crashed again. The canker comes from pigeons, it doesn't live long in the environment but does well in water or moist food. I switched her over to Medizole, which has Ronidazole 10%. She seems to be doing better on that one and that is a newer drug from what I understand. Has a wide safety margin. If you need dosage let me know. Hopefully that won't build resistance but if it does, I have another one coming in the mail - not in the zole family and kinda expensive. I would suggest trying one of the other four zoles, and I learned you have to keep switching them as they become resistant. I've also been giving her ProBios to try and avoid any secondary infect. Watch her drinking - I read one where they cured it by pulling the water and only offering it 2x/day - looks like that's what I'll have to do otherwise she drools it all over and her crop becomes a water balloon. You have an advantage in that she has not lost a lot of weight. Get on top of it and stay there, it is a long treatment. (My fight is still ongoing).... BTW, don't try to remove the lesions. When they are ready to, they will fall off on their own. In removing them you could open a sore and she will bleed or worse yet, leaves it open to more infection for something else. Has to heal from the inside. I tried all the iodine stuff - everything. Does nothing but stress her out. No advantage gained there by doing that.