Im new to beekeeping this year. I have two hives, one in my backyard and one out at another property outside of town. I just went to check on my out of town hive today and found that the colony was gone. there were a few stray bees hanging around (maybe 10 - 15), but, other than that, there was no trace of them. When I opened the hive I found a few dead bees but not more than you would normally see in a hive. There was no active brood left behind and no honey in the comb. I found some worms/maggots in some of the comb and a fair amount of small hive beetles in the top feeder which was almost completely empty.
Can you help me figure out what happened? Id really like to know if it was something I did so that I don't make this mistake again.
I'll lay out any recent activity that could potentially be significant -
I checked on the bees last Monday, 8 days ago, and the hive seemed pretty active. Its a fairly hot hive so I used a combination of smoke and honey-b-healthy infused syrup spray to keep them tame. While there, I took two of the brood frames to put into my other backyard hive which has been struggling due to the amount of adult bees that died in shipping. So far, the new hive seems to be doing great with the new brood. While at the old hive I also repaired some comb that had been out of whack due to 2 missing frames in the brood chamber. I had also recently added an additional deep super and was trying to get them to draw comb on the frames (never accomplished this). One big mistake I made was that I accidentally shook one brood frame off before checking thoroughly for the queen so it is possible that I left her outside of the hive.
I also added a top feeder to give them honey b healthy infused syrup and a megabee patty to try and encourage them to draw comb in the new super.
I have noticed small hive beetles in this hive for some time now but they seemed to keep them mostly in check and the SHB population seemed to be fairly low the last time I check on the hive.
Pictures of some of the hive attached - notice the frames that have bee carcases still in the comb, the worms/maggots, and the almost fungal looking powdery bits on one of the combs.
With the photos and the information provided, can anyone take an informed guess as to what may have happened to this colony?