I'm not familiar with the set-up of your tub so this may be wrong but when I have this problem, I shut off the tub, unscrew the filter cartridge that the circ pump suctions from, stick a hose down as far as it will go, turn on the water high blast, let it run 5 minutes, turn the tub back on, let it run a few more minutes and usually the problem is gone.
You can also use the panel to cut off the circ pump mannually and do the same thing, I just don't like changing my settings.
Hope this helps...
Drewski