I am starting to think my bin is becoming acidic....how to I balance out the pH?
Your bin is not becoming acidic. I am convinced that the whole acidic thing is a myth. If you have been moistening your bedding with vinegar, then MAYBE....
In any case, ground egg shells are a good addition to the worm bin. They provide both calcium, and grit for the worms.
Pulverized egg shells
stop feeding, fluff up the bedding so oxygen can circulate and add more carbon rich bedding eg shredded cardboard, newspaper etc