Started 2 nucs in early June and they have been building up nicely with 2 brood chambers top filled with honey and bottom with bees and brood. I have worked with them only about every 2 weeks for inspections and found them gentle and easy to work with. Put on honey supers about a month ago and today I went to put on a bee escape to remove in a day or so for extraction. The minute I lifted off the inner cover it was like I had flicked a switch, they all started a loud buzz and heads up then boom after me stinging like blazes!! I am not sure what is going on as we are not in a dearth and have lots of nectar coming in and I was gentle in my handling.
Looking for suggestions as to what might be going on here? Any thoughts appreciated.