Diseased Murk-Eye

During Children's week I had to take my orphan to the lighthouse in Westfall. I didn't realize I hadn't done the lighthouse keeper's quests with this character yet . So I went back the other day to finish them. But to my surprise, when I fought Murk-Eye he whipped up this weird disease which I swear he did not have before.
Luckily I do my questing solo so I didn't really have anyone to shoo me away in my diseased form.