A small amount is fine.
Too much protein in chicken feed results in an ammonia smell in the hen house as the excess protein is expelled in the chickens' feces and goes to waste. That by the way is why your eyes burn when driving by a commercial broiler house. But that a layer house smells completely different.
I by the way like my chicken eggs with dark yellow yokes and a fishy note.
But what the hey, if everyone liked the same thing most of the ladies would die old maids.
The actual amount of fish meal that you use should result in a final chemical analysis of 16 to 18 present.