Purple B2P With Extra Unexpected Pop

I'm inflating several balloons for the upcoming birthday party. I already have a lot of 17 inch crystal balloon inflated. Now it's time for one more! I inflate a 17 inch crystal purple balloon. It quickly increases in size, and I want this one big! As I inflate the purple balloon, one of my other already inflated balloons, unexpectedly pops, and kind of scares me, but I keep blowing! Before I know it, the purple balloon over-inflates. Pop!