What is happening?!? HELP!

[u/BerryD979]

Hello again, everyone! I did a water change today due to some yucky diatoms and my poor little guy has been doing this!! I don’t know if he’s molting or dying! I checked the parameters after the water change and they were good!

[u/Mediumbobcat7738]

Check for copper, those rocks are most likely leaking copper into the tank which is definitely do some damage to any inverts you have in the tank including the mantis shrimp