Diseased Bird: Not Eye Disease

I first observed a bird in this condition in August and took my feeders down thinking they might be spreading the disease though I cleaned them quite regularily. I still see lesser goldfinches with this with this condition. Needless to say it kills them. I’d very much like to know what is wrong with them and whether or not I should leave their feeders down or can replace them.

In case it’s not evident, the growth starts at the beak.