I have to profoundly disagree with your "conclusion". I have had none of the problems you describe, using Mills under the light feeding schedule topping out at 14ml/gal of A + B and the recommended amounts of Mills additives, I have had amazing bud sets with roots so prolific they are nearly...
Thats a tough question, the default answer is No. But there is conflicting data and opinions about using SM90 with beneficials...
Allegedly you can run them both but I would not simply because if you are going to develope an opinion on what works you need to try them out, 1 at a time, and...
First and Foremost... I would throw that bottle of super thrive in the trash. Superthrive has hormones that cause your buds to delay and stunt during flowering, they use these hormones to "prolong" the blooms of decorative flowers such as Roses etc. Madfarmer makes a good B1 and so does RAW...
In a sterile system... Disassemble, hot soapy water with 1/4 cup per gallon bleach and a never used toilet bowl brush... Add elbow grease and VIOLA clean system.
Consider using larger return/drain plumbing to add insurance against overflow... I am using a 2 inch return on my setups but this also depends on your flow rates... 1.5 inch is probably perfect for two buckets.
To combat pythium and other root dwelling nasties... Make sure you get one of...
Like everybody, I too am constantly searching for the "best" way to manage my time, garden, money, and most importantly the returns on those items.
Of course to each of us "best" translates to quite a different picture for layouts, methods, products, and Over-all anal-retentiveness.
I haven't...