I have a 75 gallon, 40 gallon breeder, 20 gallon long and a 6.8 gallon beta tank. My question is my 75 gallon and 40 gallon ph is always so low. Sits around 6.2-6.4. The 20 gallon and 6.8 are always around 7-7.2. They all have similar plants and substrate, eco complete and floramax. 75 gallon and 40 have a very small piece of mupani wood ( under 6 inches). The 20 gallon and 6.8 have cholla wood. PH out of the tap after 24 hours is 7-7.2. Water changes are done weekly, usually around 25%. I just don’t understand whats causing the difference in ph. Also, this has been on going, it’s not new. Any ideas?