I'm having a similar problem here
http://boards.cannabis.com/plant-pro...ml#post1867319

One way to find out if you have and excess of calcium is to leave a sample of your nutrient solution out for a few days. The sulfur in your nutes will pricipitate with the calcium and form gypsum( Ca(SO4) 2(H2O) )(drywall).
The solution will be cloudy, and white dust will settle to the bottom.