Did you open the Flow frames in small sections, or the whole frame at once? Did you open more than one frame at once? Did you see any honey leakage from the bottom of the hive? Did you see a lot of bearding after you harvested?
One thing that has come up in the Forum many times is that the hive can get flooded with honey if you open the whole frame in one go. The problem is that the Flow tube develops an airlock, which pushes honey back into the hive. It then drips over the brood box, drowning bees if there is a lot of it. Most people now open frames in 20% sections or less, and wait 5 mins or so before opening the next section. That helps to avoid the airlock problem.
I would inspect the hive again in the next day or two, so that you can see if the queen is alive and if you still have plenty of bees. I hope everything is OK, but please let us know, and we will try to help more.