So flush with plain water and add the MC, epsom, calmag, kelp, humic and B1 to the res? Any amount for the help, humic and B1, or just what the bag says?You cannot mix silica and calcium together at strength. Always mix silica in the water first and give 15 - 30 minutes to bond to the water add the mega crop and then the calcium then beneficials. Too much free silica can wrap it self around the calcium slowing down the calcium uptake
Your well water is a big wild card it could be all Mg? or just really soft water. It makes a difference in your nutrient ratios.
It looks like a calcium problem but I don't think the problem is stemming from the amount of calcium present but more an inability to absorb it.
When was the last time you calibrated your PH meter? When was the last time you did a flush?
I would do a good top flush followed by 2.5gMC, 1g Epsom Salt and .5 g calmag/gallon & Kelp, Humic Acid and B-Vitamins