I used to grow 'Flower Parade' and it opened normally, but 'Calgary' was a double white which would rarely open here. Probably not the answer you want, but I just ended up getting rid of it.

I can't really say for sure if this helps or not, but I have some snowdrops which tended to bud blast which I moved to a warmer spot. It seems counter intuitive but they're a little earlier in the more sheltered spot and maybe blooming earlier helps them avoid warmer nighttime temperatures or something.

...Or they just took two years off from the bud blast and it's back to failure next year lol

I have only one double which I always thought was Replete. But now that I see Flower Parade,

I think that may be what I have. Had them for over a decade and other than the first year, they've always broken my heart. I get minimal buds - 3 or 4 from the original dozen - and they usually fall off before they open. But even if they don't fall off, I have not had any open for years.

Once I figured out it was bud blast, I started cutting them and bringing them indoors to open.

This year there were 4 buds so I cut two. The two left of the plant eventually dropped off but the two inside opened beautifully.

I'm going to replant Vinca in this bed and keep this -as dry as possible- this season....to see if it's a irrigation issue. Here's a pic when it's blooming like it should...sigh. 2 yrs in a row now

https://www.dropbox.com/s/krqh1aay4vrco86/IMG_6022.jpeg?dl=0

Checked a spot where I also planted some clumps of this - this area get's no annual plantings and not irrigated. Same bud blast so I suppose it's not H20 is not a issue

Probably going to just redid this entire bed out and redo. It's not that easy just cherry picking out what is Tahiti and what is flower parade