White frosting inside my honey jars — is it spoiled, and why only some jars from the same batch?

Second year in İzmir, four hives. In August I bottled about sixty jars of my summer honey — mostly cotton and thyme from what's around us. They sat in the pantry and now half of them have white marbled patches on the inside of the glass under the honey, like frost feathers or streaks. It looks a bit like mould and one customer already messaged me a photo asking if it's safe. The strange part is it's the same batch, same day, same extractor, and some jars are perfectly clear while the one next to it is frosted. The honey itself is starting to go firm in all of them. Is this spoilage? Is it something I did at bottling? And is there a way to stop it happening next year, because it makes my honey look bad even though I know it's good.