If you are positive about increased PMS, then surely you had a higher than
normal
infestation of Varroa mites and/or tracheal mites.  Did you change your
treatment program for the mites?  Either time of year or the chemical used?

PMS is a thing not easily described to some people.  It is best described as
the
illness that is caused by the injuries suffered by the bees from mite
infestation.
An example of this among humans is cancer, but all cancer patients "cause of
death"
is the secondary infection such as pneumonia, renal failure, cardiac arrest,
etc., but
never CANCER.

Did you TEST for mites?  How often and when?

I hope I have helped.

George Imirie