Take the venturi out of your setup and inspect it for calcium deposits.
When it gets clogged with calcium, it changes the air intake characteristics.
Most times it will cause your skimmer to overflow with clear water when fully clogged.
In your case, it sounds like it's partially clogged and allowing enough air bubbles through to get what I see in your pictures.
To be clear, I'm talking about the venturi assembly, not the airline going to it, nor the volute on the face of your pump.
The venturi is the piece which slips into the face of your pump and has a nipple for the airline to attach to.
When it gets clogged with calcium, it changes the air intake characteristics.
Most times it will cause your skimmer to overflow with clear water when fully clogged.
In your case, it sounds like it's partially clogged and allowing enough air bubbles through to get what I see in your pictures.
To be clear, I'm talking about the venturi assembly, not the airline going to it, nor the volute on the face of your pump.
The venturi is the piece which slips into the face of your pump and has a nipple for the airline to attach to.

