Millipedes chilling just under leaf litter?

Hello, I hope you're all well!

I have two rosy legged millipedes from cameroon, they're large sub-adults about 13cm long. I got them together, and have had them about a month. They're my first millipedes.

For the past couple days they've both just been chilling directly under the leaf littler layer, in what looks like two shallow bowl-shaped dents they've dug into the substrate (currently about 15cm deep, I plan on increasing its depth like ASAP. I was told they were only ~10cm when we ordered them).

They're definitely alive! Their legs are wiggling towards the centre of the spiral when I disturb the leaves! Humidity is good, soil hydration is good, I give them treats (with protein) every weekend.

Just...is this normal?

They usually spend most of their time sleeping under the leaf litter during the day, and crawl/climb at night. But the past couple days have just bed chilling in what seems like the same spots.

Normal? Moulting?

I haven't been able to find anyone else keeping these particular fellas, so I'm not sure where exactly to look.