Skimmer Fluctuating

[MarkoD]

I've had my skimmer for about 6 months now. its a vertex in 250

it worked great up until couple weeks ago. i am unable to dial it in, it seems like most of the time the bubbles dont even reach the top of the skimmer cup.

and sometimes the bubbles fill up the cup and just sit there.

the foam seems too thick and the bubbles arent bursting it seems

any idea how to fix the issue?