Where are my scarlet hermit crabs???

[Ice Man]

I have 3 scarlet hermits in my 30g tank, at least I had them for past 7 months. Recently I realized that I did not see them in a while, about two weeks. Where they can be? I don't see theirs shells laying around, they completely disappeared. Any thoughts on that?
They would hide before for a day or two while molting, but never all three of them at the same time.
They disappeared about the same time I upgraded lights from power compacts to LEDs.

 

[Phranque]

Mine are mostly nocturnal, but I see one every once in a while during the day. Grab a flashlight and carefully check out your tank a few hours after the lights have gone off.

Do you have extra (larger) shells for them to move to as they grow? If you don't, they won't make it very long out of their shells while looking for new ones......

 

[Ice Man]

Mine are mostly nocturnal, but I see one every once in a while during the day. Grab a flashlight and carefully check out your tank a few hours after the lights have gone off.

Do you have extra (larger) shells for them to move to as they grow? If you don't, they won't make it very long out of their shells while looking for new ones......

I think they are gone! I found two out of three shells - empty! Why so suddenly and why all three at the same time.
Yes I have entry of larger shells for my crabs, I don't think that was a problem.

 

[Ingy]

I have various different types of hermits in my tank. The red tipped and blue tipped ones are the only ones I see out in the open. My blue, Scarlet, yellow and halloween tend to stay more hidden in the rocks and crevases. The upgrade to more intense lighting may have sent them to shadier areas now. None of them appear very active at night either, so that might not help find the missing guys.