Justin,
Any needle wheels skimmer I have ever owned plugs up inside the nipple! Thats ASM, Euroreef, Deltec and the list goes on.
I am thinking you have salt residue in the nipple where the air enters the pump chamber.
Take the pump apart and shin a flashlight down in that hole and get it at a angle so you can see down in there. If there is any white stuff at all(salt, minerals, debris you are going to get a drop off in skimmate production!!
Plain and simple. I have cleaned mine and after it's a whole different skimmer.
Once it has been cleaned out well, you can let the air intake suck up a cup of HOT RO DI water once a week or every other week. This goes a long way in keeping the air intake clean..........