Perhaps too much chlorine? Let your starter water sit out over night.
I'm assuming you are following the temperatures in the rehydration protocol and have a starter solution that contains plenty of sugar and nutrient and then you are only pitching it into the must when the temperature difference is only 18 degrees?
I live in florida, central florida actually. The yeast starter was about 105 Degrees when i made it. I let it sit for 2 hours before I introduced it. So both were room temp, about 77degrees.
I don't use tap water for my wine or yeast, spring water only.
Starting gravity was at 1.070 per the recipe.... I had a hard time doing this, I usually start every thing at 1.120. yes I like my wine with a kick.
My first batch I used a blueberry lees, it was incredible. I have friends that aren't wine drinkers and they want me to bring this stuff to parties.