You guys are doing great, it's all perfectly normal what is going on now!
Once you get to know her patterns a bit better, you may be able to anticipate days like today-- even today, you kind of knew at the PMPS that you were going to see some downward movement. Many have found that feeding a small LC meal early on can slow down these drops-- so, maybe next time, if you see at the pre-shot that it looks like a bounce might break, you could feed a small meal at +2 rather than waiting for the number at +3 to trigger action.
It's all part of the (steep) learning curve with this, but, really, you are doing fantastic!