I personally would drop the superthrive....you have grow nutes and I think that should be enough along with your CalMAg. LK is good stuff....I myself would like it out of the picture until the problem is pinpointed but its up to you. I like to start with very simple and work up.

40 gallons of water is alot....hope its next to something easy to empty and fill it from.
I actually had a 25 gallon res for my 8 plants and even that got to be too much hassle with the water so I moved down to about 1/2 size growing area because of it.

Buy yourself a nice LARGE plastic trash can and lid and you can store your RO water in there. We keep our huge barrel of RO water outside with an aquarium heater and that works great for us. At some point if your hydro systems leaks or becomes contaminated or something (god forbid) you may need to have 40 gals of good water ready in a hurry. This will probably help if you have a place to put it and keep it ready.