Build up at waterline.

I am getting at light brown to yellow greasy build-up around the water line on my spa. Chemical levels are within limits. I have bought several spa flush products and flushed to spa 3 times. This build-up is greasy and sticky. I am at a loss. I removed the lines going into both pumps and I don't see any build-up. The main circulation pump is starting to make some noise and I was wondering if I could have a seal or bearing going bad leaking oil or grease into the spa. I ask some at a pool supply place and they didn't thinkthat could be the problem. Any help would be appreciated cause I am at a loss.

I am not sure what is causing but I would try a enzyme product. Also you may want to use a scum absorber to see if that makes a difference. I don't see how a pump seal or any of the mechanics in the spa could cause this build up.