In pots or in the ground, and in sun or shade/partial shade?

In pots / full sun

The usual reason for flower buds aborting in summer is insufficient water - it may be you just didn't give enough water often enough, and the plant will sacrifice its flowers as a survival mechanism, especially in full sun during very hot spells, they would have needed watering twice a day probably.

The other thing is, if the plants have been in the same pots for two or three years, they may need potting into something larger - as the roots expand and fill the pots, there's not enough potting medium to hang onto enough water for the plant, so potbound plants need really frequent and copious watering.

OK! Thanks very much for your input! ?