So...
I replaced the blended blackberries with new fresh ones. Fermentation was executed without abnormalities.
I have the Elderberry/Blackberry in a carboy now. Although I am a little upset with myself because I had to top off about 3 quarts, I used water, and I am afraid that may dilute it too much. But...on first racking (from the primary) it tasted just fine.
I used the "bad" blended blackberries to make a gallon, just to see how it would turn out. Holy cow! It has a bitter undertone, like an orange rind. I am so glad I got those things out. Thanks to all for your advice!
I will probably wind up posting how the two wines turn out at next racking.