If it were me I'd save the vet money. A vet will cost a decent amount of money for a very simple problem. If it gets worse or red and infected looking then I would go. But going so early seems like a way to rack ip a bill u don't need.
Sulfur is a deterrent but not a 100% guarantee. Elemental sulfur is not generally toxic, but I do not know how much would be to much. I don't think a chicken would eat too much to hurt it.
do you have more pictures of your project? what things still need to be worked on? looks like the double tail needs a little work still. The bird in the picture is gorgeous.