I got some insight into bloomout this year.  I have been keeping temerature records for some time and co-ordinating it with rebloom. Some very interesting information was learned from this.

Bud set, that is the  diferetiation of  the growing tip (apical Mersitem)  from producing leaves to producing  flower parts has a very specific temerature requirement. Once bud set occurs, the plant increases now start to grow. This is a a result of removal of  the  growth repression control (apical dominance)  that is exerted by the growing tip. Once it is in the stage of flower bud production this repression no longer occurs.

Temperature requirement is that minimum night temperatures are in 15-21C or 59-70F range for about five nights in a row.

Last year we had cool nights and did not get the required warmth at night needed for bud set (at least not for most cultivars)

This year there was lots of bloom in spring but no increases, so lots of bloomout. Obviously there was a secondary bud set as a result of  winter vernalization, but it didn't  trigger  growth of increases( or increase set) the same way that  summer temperatures did.

With you the problem would be having cool enough  nights as versus my problem of having warm enough nights. But same result.

 If you have a weather station near you  you could check on minimum temeratures. Or I could look at it. Just let me know of weather station nearest to you with recorded temerature data.

The critical temperature varies from cultivar to cultivar, depending on it genetic inheritence from species.

Chuck Chapman