Reapplying to a previously accepted Ph.D. program, will this be considered rude?
It is possible you don't need to reapply to B and C. Here was my experience:


Applied to uni A and B, got offers from both
Accepted offer from B. Rejected offer from A.
Attended B for one year, decided to transfer/start over at A
Contacted uni A. They were happy to accept me based on the previous application. I didn't even have to reapply, they simply considered it deferred matriculation.


I don't know how typical this is, but it may be something to discreetly look into. Maybe you know an administrator or faculty member at B or C that could give you the inside scoop.