They told you your stabilizer and cal was low? Your stabilizer is HIGH and vinyl pools do not need calcium. With your CYA at 120, you need between 8-15 ppm FC to remain normal. You need 25 ppm to shock but I don't know if that would be good on a vinyl pool. I would think about draining 1/2 of the pool to reduce your CYA level some. See this thread to see what you need to maintain your FC at with your CYA level. http://www.poolforum.com/pf2/showthread.php?t=365