I have a 50 Gal aquarium with a few Betas in it and 2 banana plants. I noticed ammonia starting to build so i tested my PH and it was reading below 6. I did a 50% water change and waited a few days and tested it again and it was still below 6 so i did a 66% water change and the next day it is still below 6. i have tried chemicals to increase PH but still no change. My tap water is reading at 7.0 ~ 7.2. Ive never had an issue with PH before i know bakeing soda could help but im hoping to find the root cause of this.