I had chicken thighs in a Puttanesca sauce (olives, capers, tomatoes basically) and some rosé wine..... I didn’t realise that the reading could go down.
Readings fluctuate up and down throughout the day and night, depending on what we do or don't eat, and lots of other factors, from amount of sleep, exercise, stress, medication, and even the length of time it takes to digest food.
Your 6 and 5.7 are great, and it shows that your meal didn't cause a rise - which is great.