Like mc, I suspect you may have a battery problem, which can mimic or cause a charging problem. How old is that battery? Was it subjected to going flat due to failed alternator(s)?
As for the chance of three failed alternators, it is better than you think. Inexpensive “rebuilt” or “reconditioned” alternators often fail. The re-builders or parts store will generally replace it with another for free, but the replacement is just as suspect as the first one. You have had more in a row than usual, but it can happen.