Is my math correct that I would doze KH2P04 and Plantex CSM+b will be 1.041ml??
and the 1/8th a teaspoon for k2so4
There is already enough potassium in both the nitrate and phosphate solutions for most tanks. So skip it unless you see signs of potassium deficiency; small pinholes in older leaves, bordered by yellow, that grow larger with time. It is to me the most easily recognizable deficiency.
Your CSM+B dosage is correct.
Your calculation on the KH2PO4 appears to be 50% too low. Assuming you followed Rex's instructions, you have 1.5 tsp. of KH2PO4 in 250ml of water. The dry dosage I calculated for your tank is 0.0125 tsp, so number of doses is:
1.5 / 0.0125 = 120
And dosage amount in ml:
250 / 120 = 2.083
There are many ways to approach mixing and determining dosage for liquid solutions. I went through the math with you rather than a simplified method, because once you understand that, you can figure it out any way you like.
One thing you might notice is that all the dosages are exact multiples of each other:
CSM+B = 1.041ml
KH2PO4 = 2.083 (2x as much as CSM+B)
KNO3 = 4.166ml (4x as much as CSM+B)
I doubt that's a coincidence, but rather a peek into Rex's personal dosing preferences and calculation methods.
If you wanted, you could put half as much KH2PO4 in a bottle, and a quarter as much CSM+B, and then you'll be able to dose the same amount (4.166ml) for each solution. They'll also run out at about the same time. There's also no harm in rounding up to an even teaspoon (5ml) if that's more convenient than a ml syringe.