It is somewhat normal. It happens to blueberries, remove flower buds. The cold summer is somewhat to blame. Most growers are seeing this happen including me.
Blueberries are super hardy, you have no worries as long as you overwinter properly for potted blueberries.
This trait was enhanced for the Sweetheart cultivar. They found a way to exploit it, and this cultivar produces a fall crop, besides a summer crop. Although the fall crop is small. Many cultivars will produce a small 2nd crop if the weather was right. One reason it happens is many blueberries have southern blueberry in their lineage and those can fruit twice a year if grown in extreme southern regions.
Vaccinium corymbosum 'FLX-2' P.P.# 19,381 (Bountyfull Blue) has low chill requirements and this cool summer, it met it's requiements so started flowering. It is a plant that favors southern regions. Not the best to grow in colder areas although it should do ok. It is a Southern Highbush. For zone 6 Northern Highbush grows better. But many cool SHB plants around. I have 2 myself. This one looks interesting too!

This post was edited by Drew51 on Wed, Nov 19, 14 at 8:45

Thanks Drew51. My other 2 bb are northern high bush &they are dormant. All 3 containers will be left outside on my balcony. I'm in a condo & can't put them any other place.

Some things you can do in the future. Transfer them to fabric containers. These breathe better in the winter. The root pouches at greenhouse megastore are cheap.
Some Southern Highbush try to retain their leaves, so in colder zones they fall late. Kinda shed all winter. Keep us updated on how they do. A row cover or burlap rap might help keep winds from drying them out. I use leaves and burlap on my blackberries. Some are barely hardy in my zone. Often the canes die, but the crown lives. Which means no berries! So i started protecting them and it has worked well. Some I just cover with leaves. I'm finding though that leaves are messy, hard to keep in place. The row cover or burlap helps keep them there, and adds more protection. The biggest problem is when they freeze and thaw. You want to keep them frozen. Burlap would keep the sun off of them. Row cover would not. You could tie it, and it would not look bad. You could try without it, and if you lose a plant or two, next time use it. Experiment.
They might not need it.
Anyway just to go over the freeze-thaw is your biggest problem. You can keep them warm, or keep them cold. Cold is easier in zone 6a
I have 4 in pots, but are in a garage, so protected from extreme cold, wet weather and drying winds. The fabric container would dry quicker if wet. another problem with pots outside.
I also have 3 in raised beds. The ground protects the roots, here is Toro NHB today.
{{gwi:54345}}

Here is Chandler (raspberry canes behind it)
{{gwi:54346}}

This post was edited by Drew51 on Fri, Nov 21, 14 at 7:44