Crabs killing / eating each other!!!!

Well it looks like my white leg hermit crabs & my blue leg hermit crabs are killing / eating each other, since I got my tank set up 4 months ago, here and there I see left over crabs on the rocks & sand bed, I do see them grabbing each other, I started with 20 white leg hermit & blue leg & I think I have now 10 to 8 of each, my tank is 110G with about 90lb of live rock, don’t think it’s a food problem because I’m the type that likes to feed my fish I have to control myself
So what is it, is that how crabs are & I will need to replenish them every few months.

Do you have any extra shells in the tank for the crabs who are looking to upgrade? They might kill other crabs/snails if they have no other options available and need to upgrade.

+1 Lizard... or you could just have a jerk crab. I had a huge blue legged one that got banished to the sump because he just liked the hunt.

I need to get extra shells, thats what ill do

Or they just died of natural causes, and the parts that you see are just their molts, which look incredibly like the real deal. I've seen mine fight, too, though.

I had around 20 hermits in my 45g. I kept count of all of them at first. Then over the next months, it dwindled to half. I now have 2 of the original. Never replenished them Heheheh. I think they just died on their own.

Its what hermits do: fight --usually over shells.