Always mix
Calmg first. The order goes Silica -->
Calmg ---> A/Micro ---> B/other parts if 3 part nutes. Ca is not friendly with the nutes in the B formula. All A/B 2 parts nutes put all the Ca in the A exactly for this reason. Mixing them out of order can cause issues with lockup and you will see some of the issues you are seeing.
If your using tap you prob don't need
Calmg. Think of
Calmg as a band-aid. It's there to correct problems and works 10x better as a foliar then in the nute solution. Stuff Like Canna, GH, H&G,
Botanicare (CNS/Kind) ect all pretty much have enough
Ca/Mg in them on the base you dont need it. Canna doesn't sell a
Calmg product exactly for this reason.
Ca/Mg problems are gonna be the first thing to show their face when having a PH issue in the medium. Doesn't mean you don't have enough. Just means something is out of wack on the ratios usually from a PH issue. Also if you have high PPM/EC tap (which will usually have high Ca) and then you are adding
Ca/Mg on top plus the base Ca in the nutes (which is higher in Coco nutes) you can/will start locking out Mg/K. Its all about balance. Remember the people who formulate these nutes do so to make it easy for you which is why you pay a higher price for them. No need to make it harder on yourself.
PPM/EC is a measure of the electrical conductivity of the nute solution. This is basically giving you a measurement of how strong the chemicals are in the water so you can get a target of what to feed and hit a certain range. Important for tap water so you know where your base is starting from. Your tap 400 ppm? you would feed them a lot less of A/B so you dont over nute them. Kind of a lot to take in on the first go but the more ya know the easier it gets.