Hermite crab dying/dead... help

Hi All,

I am fairly new to this hobby and have just finished cycling a 10g nano. Yesterday I added a peppermint shrimp, emerald crab and a red legged hermit.

After acclimating them and putting them in the tank after about 5 hours the emerald crab was on his back and the hermit crab looked fine and was moving around.

After a few more hours the emerald was back upright and moving and the hermit cam out of his shell, rolled onto his back and looked like he was trying to molt?

I left them over night and the hermit is still out of his shell and now there are no signs of movement at all so I am assuming he has died? The emerald has stayed in the same place all night but appears to be moving.

Oh and the shrimp has stayed in hiding but seems to be ok.

What could of happened here?

Tank specs:

Amm - 0
No2 - 0
No3 - 10
O2 - 10
Alk - 8
PH - 8
Salinity 1.0245

I checked with my LFS and their salinity was at 1.025 so not far off of mine at all.

Any help would be greatly appreciated! I have left the hermit in the tank in the vein hope he is malting and may get up and move still....