Check the TDS of the water you get and see if it's zero or near zero. It could be that the water you're purchasing is suplimented and may already contain calcium.

It's my belief that calcium is necessary throughout the plants life. Better late than never in my opinion.

Just wanted to add that the micro has calcium in it, so you are providing it, however, if the water is RO water, then the micro needs a little help...ie...calmag+

GM