Rising pH falling sanitizer

Hello everyone,

We just bought a house with a hot tub and I'm committed to taking good care of it. I have done my research and have a Taylor test kit. Judging by my initial tests the previous owner used only stabilized chlorine. Our CYA levels were off the charts even after a half dilution test. I drained and refilled; I estimate I renewed 3/4 of the water. My Taylor reagent test kit now shows about 50 CYA while Taylors test strips show nearly zero.

Since the refill my chlorine (bleach) levels are losing nearly 2ppm a day and the pH is rising by nearly 0.2 a day. We haven't used the tub since the refill. It has been a week since the refill and this is continuing. I'm adding pH decreaser and bleach nearly daily and this doesn't seem right. Can anyone shed some light on what's happening?

Values per the reagent test kit:

Alk: 90

CYA: 50

Calcium Hardness: 190