I got a couple of double blooming tuberous begonias and they had double blooms for a while but they are now coming up as single. I've been pinching the side flowers as the buds emerge in order to get the main female flower to be large. The plants seems very healthy though, keeps growing and putting out new buds. Is this just a normal thing? Is it because of the heat? They are under an overhang in the front so they don't receive direct sun but do receive bright reflected light. They seem to like it that way.

What should I do?

(Also, has anyone noticed that begonia flowers taste citrusy... don't go around eating them just cus I mentioned this, lol).