the are looking great. Once they have been pollinated by a bee the white flower will shrivel up and turn brown. Soon after the blueberries will start to develop and swell up.What variety do you have?
The white 'petal' part dropping is fine as long as they are leaving the small developing fruit, which looks like the case with yours. This indicates the flower has been pollinated. You only need to worry if the whole flower/fruit and little bit of stem are dropping off. They will appreciate a liquid feed for ericaceous plants once a week from now until the fruits form and best to only use collected rainwater to water them as some tapwater is quite hard which they don't like.
I have those. Goldtraube is one of my top favourites, bluecrop is your average blueberry taste, although this year not producing as well for some reason. I'm hoping for a late boost. Haven't tried bluegold yet, new addition this year however after reading reviews it has gone to the bottom of my list. Fingers crossed but I haven't found anyone call it their favourite yet..