Frozen Shrimp Quality Issues: Red/Black Discoloration & Strange Odor

We have observed the following situation: the freezing method used is water freezing, which has resulted in the entire box of goods being frozen into a single entity. All the shrimp are in a frozen state, with the shrimp bodies being hard. However, some shrimp heads and/or bodies have turned red or black, and some boxes of goods have a strange odor.