I'm in the same boat (on day 4). I was going to change out the water again tonight. I'm using distilled water and PH down to 5.8 - 6.1. Leaves are starting to lighten quite a bit so I was wondering about adding that calmag but I was under the impression that you don't add anything if your using distiled water. If you using tap water you should add Final Flush to get rid of PPMs from the tap.