Well water with pH of 4.1 and almost 0 KH and GH
I noticed when I do my water changes my pH drops almost a full point. My tank runs between 5.10 and 5.75 pH. The water out of my tap is 4.1 according to my probe. I am keeping one GBR, three oto's, a couple of ghost shrimp, and an assasin snail to combat the unknown number of MTS's. I have a flame sword surrounded by HC with eco complete in a 14 gallon biocube with 6500k bulbs, uv sterilizer, pressurized CO2- all controlled with a neptune apex lite. I am regularly fertilizing with Seachem Flourish line of N, P, K, and Comprehensive. I am using the Apex Lite pH probe to control CO2, however my drop checker never turns fully green. I have the pH control set to turn off the CO2 when it gets below 5.10 pH. At night the highest the pH gets is 5.75 (CO2 and lights off). Fish and shrimp seem to be doing fine, plants pearl well but seem to be slow growing. Is the low pH stunting my growth, or should i allow my pH to go lower than 5.10 to achieve higher CO2 levels? Should I add to my hardness/ buffer for a higher pH? What is the best way to do this without constantly chasing my tail.