Hard COral Diseases?

[Nexus13]

I really want porcelain crabs in my tank but they don't seem to survive.

I tried one from big als first,
after the drip for 3 hours it died within about 2 hours of being in the tank

then on my second attempt i bought 3 thinking it was maybe an unlucky crab and dripped for longer. One died in the drip chamber, the other two died after about 2 days.

definitely something abotu my water conditions that is killing the crabs.

I'm gonna invest in a slew of new test kits to get a better idea of what's going on with my tank.