Normally the oils cause a skimmer to go nuts. I think the new canister is coincidence. My guess is you have some salt creep built up in the air line. Reove the pump and the piece where the airline connects. Clean the pump of any sludge, remove the airline and look in the hole. Rinse or soak in RODI
water and maybe root around with the tip of a straightened paper clip. I have a Coralife skimmer that always gets salt build up right where the air line connects.