Kenni Judd wrote:
As a precaution, I would certainly isolate the plant until you figure out
what's going on.

Without more info, I can't even hazard a good guess -- I assume that you
have looked (on the undersides of the leaves) for and ruled out insects
[scale, mealybug] and mites as the culprits?

Yes, there's nothing that can be seen, at least not with the naked eye.
The problem hasn't gotten any worse since I first posted here, but it
has not gotten any better either. The blooms seem as large as normal,
the colour seems normal, although they are not as numerous as last time,
when I got three stalks of blooms. This time only two.