If you haven't sorted it out yet I would suggest you check the needle and seat. I have been doing carb work for 35 years and I have found that problems like you describe start there. Is the seat tight in the carb, does the needle have any sign of a ring imprinted on it. If so it's shot! Make sure the tang on the float pushes squarely on the needle. Uneven pressure on the needle will cause it to leak or wear prematurely. Sounds like you have the rest in hand though you may find that when the fourth carb stops flooding you have to go up in jet size on all the carbs. Good Luck!