Saddle butterfly with sore lips?

[jassz]

So, yesterday for the first time I saw a white blob on one of the butterfly's front fins. It's really hard to get a picture, but it's very easy to see. About 3/4 inch in diameter, adn opaque white where the rest of his fin is rather transparent. Does that sound like a fluke? Or just a fluke because we've been discussing it? I zoomed in on Zoom Zoom's fin if that helps.