Whether the chickens know their caretaker/your parents isn't the issue, they knew you disappeared, and you are very important to them. You'll have to see if they resume after things return to normal. It could be the heat, but it's really hot here and mine have not slowed down at all. I am leaving for a week next month, and my husband will care for my flock. We will find out if it makes a difference, as I give them a lot more attention than he does. Maybe it will turn out to be none of the above.....