What is the margin of error on the Cal test kit?
25ppm is a good drop and indicates a decent consumption for 3 days. But if there is a larger margin of error and the test came out on the low side that could account for some of the drop.
At 8.8dkh you're going to need to dose Alk today. At the very least you should start the AFR back up, if you haven't already, and I might start with there initial instructions of 5ml per 26 gallons. Maybe a little less. Then check the cal again every couple days to ensure it's still dropping. But keep an eye on the alk daily as your in the target range now and you'll want to maintain the 8.5 to 9dkh.