One of my first grows I did indoor I used only Iguana Juice and I developed a calcium deficiency a few weeks into flowering... If your looking to keep thing organic I would recommend general organics cal mag it is derived from molasses so it will provide carbohydrates along with calcium and magnesium... And are you using a soil like happy frog with mycorrhizae and beneficial bacteria if not another thing I would recommend adding to your soil is something like Happy Frog or Dr. Earth soil amendments that both have mycorrhizae and beneficial bacteria plus an organic N-P-K boost to your soil... Don't forget to pH your fresh water and nutrient solution to 6.3