Hiding/molting?

[Atlas:)]

Hi I’ve got 3 crabs, Sushi, Perri, and Ollie. They’ve all been pretty active, but the last couple weeks they’ve been hiding under the sand. Now I had Perri do this when I first got them, but she came back out of her own accord after 3 ish days and they all continued to hang together and everything’s been cruisey. But about 2 weeks ago Perri and Sushi dug underground again, I was kind of concerned as I couldn’t find their ground access points, and after 5 days carefully dug them out, I had an iso tank ready incase they were molting. Turns out they were fine, they looked normal, there were no signs they were molting, once they were out they all hung out and ran around a bit, but they’ve gone back under again, no visible signs of where they’ve dug or hole back up to ground. Should I dig them out again and put them in an iso tank just in case? Is the constant digging and hiding a premolt thing or a sign I’m stressing them out too much?
They’re generally pretty active during the day, will go sit on branches and spend hours chilling together, or sometimes go find a corner and just sit, some nights I hear them all chirping at eachother, with my job I often come home super late at night too and always come home to find them running around or eating, so I feel like it’s a fair call to say they’re not out during the night without my notice.
Ollie isn’t a big digger, he generally just hides under a rock or something, but he’s been pretty lonely without the others and has been hiding under his favourite rock all day the last 2 days.
Idk I’m just really worried that I’m stressing them out, or that they’re gonna die while under the sand without oxygen or food/water.

[curlysister]

Stop digging them up! Crabs can stay underground for days, weeks, or even months. They don't need any food or water when they are under. Digging them up is stressful for them, and if you dig them up at a critical point in their molt, it can be fatal.

What size tank do you have? What and how deep is the substrate? What are your heat and humidity?