Adding
Calmag won't hurt, (straight from Bryce) but with
H16 it's a bit of waste, even if you are using RO and Coco, like I do. Unless you have a strain that just needs the extra kick of cal mag. I have a Skywalker that every now and then shows a lil cm def so I top dress with epsom salt. If you are using Prime, there is no need to use any kind of Silica.
Not to come off as a dick, but you can afford
H16 and not an RO? I don't get it, RO's can be found for cheap.
I haven't used Cal Mag in over two years, except between rounds when I treat my coco between rounds. I give the coco a dousing of
calmag, cannazyme, and molasses before I replant in it. This is the ONLY time I use cal mag though.