I know this might sound silly, just put a feeder jar on top. Here is what I find interesting, give the bees something to do. Build comb, feed brood, clean up comb. Normally the bearding issue goes away, even in the heat. Just what Ive noticed, we have to think in our summer its hot, no nectar coming in. no nectar no brood raising, even if the queens laying they are probably eating those eggs/larva.