My first *guess* is humidity. From your description of the way the bloom looks, it sounds like it needs more water. That said, after reading the "facts" I wonder if by chance you sprayed the blooms or buds when watering or treating with the different pest treatments? Either of these or both together could cause the issue you mention. Since I am the first to get to your thread with a response, I will say what every other senior member is probably thinking: Post up a photo of the issue and let us take a look.
Glad you are here. I hope we can help you figure this one out.