skimmer issue

I have a 75 with a 30 sump. My skimmer is an ASM G-1x. Ive been running this skimmer since i set the tank up about 15 months ago. Its been running great until about 2 weeks ago. I clean my skimmer cup every other day. 2 weeks ago, i was checking the bowels of the setup and noticed that the skimmer cup was overflowing. i emptied and cleaned it, put it back on and had to readjust it. it worked fine for 2 days, i cleaned the cup and the following day, it was overflowing again. I've been careful when taking the cup off to not mess with any of the setting for the skimmer, but almost everytime, i have to readjust it. Anybody have any reasons why this may be happening.