I agree with @Goat Whisperer...sores does not sound like MG.
You could use the Tylan 200 but it would be a mega small dose and the 50 is easier on chickens, or so I am told. It is the same drug, the 200 is just more potent. It seems that most people give the 200 orally, and the suggested dose varies but I would use about 1/4 cc given orally to a chicken weighing about 6.5 lbs
If it is fowl pox it is a virus and it will run its course.
The first two are of Mia (the original D'Uccle I wrote this thread about), and this morning her left eye was sealed shut, and her right eye looked terrible. But now she looks a little bit better, and her left eye is open and just has some gooey stuff in it.
The next two are of Sally (and her chick), and she just has a lump/sore (?) on her beak.
The last one is Susie, she has a sore on the corner of her mouth and so her beak is always slightly open.
Here are the pictures:
Her left eye is just closed in this picture,
I agree, fowl pox. MG won't make sores. There are two kinds of pox, wet and dry. Wet can be in the mouth and it can kill them by blocking their breathing. It will look like egg yolk; also can be literally on their eyeball. I lost one to wet pox; its throat was just full of it and it wouldn't eat... had another lose its eye. The dry will be scabs or sores that will just dry up. They say the entire flock will get it, but I had maybe 5 or 6 out of 30. Once they get it they are usually immune. Really not a lot you can do but wait. Much better pox than MG.