Sometimes that can be the jacks leaking down. I have a single front jack at it eventually got worse. The repair was to replace one of the valves at the pump. There are two valves per jack, one in and one out.
Next time you stop and have the jacks set, tale a measurement of the exposed inner shaft of the jack. Measure it again the next day.
Don & Mary
2019 Newmar Dutch Star 4018
2019 Ford Raptor