Matt,
I wish I had a good answer for you, but I don't.

However, you said Starlines or derivatives, and the "derivatives" might be
your problem.  The Starline is a HYBRID, developed by Dadant's Bud Cale.  A
hybrid is man-made, not a race; and hence cannot reproduce itself.  A colony
must be continuously
requeened with a "man-made" Starline hybrid, bred by a specific queen breeder.

Geneticists have shown over and over that when a daughter of a hybrid queen
gets
bred by any drone, the "bad points" like aggressiveness usually comes forth
in spades and the "good points" tend to disappear.  This is one of the
reasons many beekeepers just don't want much to do with any hybrids,
regardless of whether they are Starlines, Midnites, or Buckfast.

I did not say that this IS your problem, but I say it MAY be your problem.

I hope that I have helped.

George Imirie
Certified Master Beekeeper
Beginning my 69th year of beekeeping in Maryland
Author of George's PINK PAGES