All my colonies suddenly died
Hello, as the title says I have lost 12 colonies this winter. I have no clue why this happened.
Last year had a good yield of honey, I've been beekeeping for 3 years. I treated the hives with anti-varroa strips in late October, by then the hive was prepared for winter. All was good by then, left plenty of honey in the hives. This December was warmer compared to other years, with temperatures in range of 0-10 C, precipitation was average. I went to check them on 30th of December, I wanted to see if they have enough food and then I was shocked to see them all dead.
I would be grateful if anyone could explain why this happened.