Everyone has bad days but it doesn't mean to say you can just brush it off. If you're a manager in the office and someone keeps failing at doing their job, you would have every right to be concerned, especially when as a manager you know that person can do the job to a high level. You would notice it very quickly, address it and look at ways of quickly fixing it.
In this situation it's the mentality of Brook that is the concern (again I repeat I am not doubting his talent) and it needs to be accepted as a concern otherwise it won't ever change. He needs to adapt and understand the game situation. He needs to watch how Stokes has batted in his last two innings.
In 5 innings, Brook has faced 181 balls this series, that's not good enough. He needs to adapt quickly because it's clearly lacking in his game.
You will find I've criticised Stokes, and I have criticised plenty of his captaincy decisions this series also. However his mentality and toughness on the field is one of the best in Test Cricket and he's a captain I'd love to play for and would love as my leader because he gets stuck in and never hides.