Oven baked cod fillets get soaked in their own liquid
As the cod fillets were two different batches, chances are you just where unlucky with the second batch. Even within expiry-date, the amount of water food loses while cooking can vary vastly with age and quality. And even good fish shops can have watery batches at times.  

To generally avoid this soaking happening, I would rest the cod on a cooking grate or - this is a personal preference - on some pre-cooked potatoes.  

A small factor may be oversalting, but chances are it is actually the cod.