RE: Why oh why?
Since that tube broke and that is the only thing you changed then my bet is the peep moved.
This is why we need to have measurements on these types of things,a quick check and you would know.
For the record,rain can slow a bow down dramatically when the string gets wet(not 12" though)but if it is well waxed,it shouldn't have still been shooting low after the first shot,unless it got soaked again.