You really have to watch out with the Humbolt formulations as most contain no calcium and most do not have all necessary trace elements for inert hydroponics. There are many good tow part and three part formulations. I would avoid supplements. Supplements are more geared towrad orgainic grows and often cause problems used with chemical nutrients. Most addittions (magnesium, calcium, iron, phophorus and potash) are really more to counter the inbalances common in recirculating nutrient reserviors that are seldom changed out. The plants do not have increased needs but the reservoirs have increased amounts of their nutrient minerals tied up in buffers thereby causing deficiencies of nutrients. They are in the reservior but not available to the plants.
The only really good nutrients are those mixed especially for your needs. However most growers have no way of determining those needs.