Rebecca, your cherry tree's symptoms sound
all too familiar... I watched one of three cherry trees die a slow death from
Bacterial Gummosis. The "worst" part was I needed it as a pollinator for two "miss-marked" cherry trees that had become beautiful - non-fruiting specimens. They apparently dodged this Bacterium, and like several "wild" cherry seedlings growing in the woods nearby, were not eventually killed by Gummosis.
I'd bet, with the "multiple grafted" tree (another problem-prone aspect of such "fruit cocktail trees"...), one or two (in your case the "Rainer") varieties will be more susceptible to this than the others. It was an easy search - I remembered it was "a bacterium" - here's a description / answer online @:
http://www.gov.on.ca/OMAFRA/english/cro ... 88-086.htm
It looks like they'll need more than just dormant oil...

and that bothered me too ~ that's why I "turned" all three of them into
Desert King Figs! They're loaded with figs and growing magnificently!! (with
no spray)