I'll definitely remove the DME the next time I brew this recipe and replace it with the 2-row. The only reason I used the DME to begin with is that I didn't have enough base malt on hand and didn't want to drive 50 miles roundtrip to get more or order online and wait two days for delivery.
And, next time I brew, I'll try mashing at 150 F vs the 153 F I did this last time.
I will try Martin's suggestion and add a pinch of gypsum to what I have bottled.
Thanks for all the suggestions and advice.