In the past, there were 3 times as many bulbs in place without a problem!


wow

so maybe your breakers aged... (I'm serious, they do age)

or you changed extension cords to a heavier guage?

or there is other load in another outlet on the same breaker

I would as a test change to a non GFI breaker to eliminate that possibility.

I didn't see the naswer to the 2 out of 3 question, what if you use 2 strings instead of 3?

Mark