Skimmer not skimming

Hey friends , I have an SC aquarium skimmer (sc-s50) got it used 3 months ago, it worked fine till recently (2 weeks) is bubbling but not skimming at all I already rinsed it and clean twice, play with water height, keep messing with the control and I can't get it to foam, all I get is a cup full of tea. I'm feeding twice, and my stock is

1 clown

3 damsels

4 chromis

1 kole tang small.

GSP small

1 colt coral.

Any feed back will be really apreciaed