??? why man if you drink your tap water its good for ya plants man, ive used the shittyest city water you can imagine (recycled 7 times min) and have always had great results...you can run fine on tap water.......
what nutes are you using? you should only need to ad cal/mag if using ro water, if not your nutes have more then enough to cover it. calmag is not a wonder product.
get the drops man its all you need.....imo your making this well complicated thats all mate, and you would have had better results if you dropped half the gear your using and put less plants in that space.
again not having ago just trying to help you run your dwc properly and get the right results when done correctly it is the biggest yeilding most productive method there is!!