One of my three hives developed chalk brood in mid August - always about 4-20 mummies between the entry, bottom board and screen bottom. I read up and expected it to clear itself, but it is continuing. The hive seems otherwise healthy, started this spring as a package. In that time I did find some mummies in front of one of the other hives once, but no signs since in that hive. We had an August/September drought, so seemingly not a moisture issue. Anything to worry about?