you tend to be wrong every time regarding show level conditioning.
So I take it that Nick had a considerable amount of more bodyfat now compared to his best showings? He never has onion skin in the first place, but a slight amount of more bloat from water can make a big difference. So imo it had to do with the carb loading and wanting to be as big as possible, not so much a dieting or fat problem per se. See what happened to Samon when he shased extreme cuts through diet, that doesn't always work either.
And sometimes the body just doesn't cooperate.