I think I would wait until the water clears up and test CYA again before I added any. It doesn’t make sense to lose that much that fast.
Also, if you do add, add only the amount to achieve about 10 ppm and test again.
I thought it was strange to lose CYA that fast like that but it makes sense if I have ammonia attacking it. My last two test (in 15 minute increments) since the sun went down has been 7.0 and 8.5 And the two bottom drains are visible in the pool which is a tremendous turnaround. I’m going to do one more test and then add 1 pound of stabilizer and test CYA before moving forward
