After reading through your journal there were a few times I was trying to understand how much water you were using , then started to look how much guard you put in a figured 2ml per gallon. (3.5 gallons on the four gallon bucket)
The 5 gallon bucket I use needs about 3 1/2 gallons or just over 13 liters I think for the plant. I normally mix 4 gallons or 15 liters and use the left over for feed the next day. I find it easier to dial in my solution in somewhat even or whole numbers when mixing.
Do you use RO water?