Betta tank PH 7.6

Just why? I don't understand. The only other thing in there is the occasional pellet that doesn't get eaten and a large glofish sculpture. All I can say is that the water smells like mold and the tank is not cycled because the little beauty doesn't make enough waste for ammonia to build up. I'm completely puzzled. I changed 50% of the water 2 days ago when it read this way. I expected to see it level out but it's the same. Can someone help me to understand what's happening and what I can do to neutralize the ph?