I'm gonna add that if you are actually sure that it's leaking from the diaphragm and not from the top, then I would suspect that the diaphragm itself is torn.

When these carbs flood, they usually leak from the top or from the trumpets, but it's not always easy to detect the leakage point because the thin clear fuel can run against the carbs side and drip from another point.

Sure if the leak doesn't re-appear it was probably the needle valves, so nothing to worry about at this point really.