Yes, you have the option of adjusting your automatic tips. However, I hope you think about this before reducing them. It's a VERY fair amount. I always leave my auto tips in place, as well as tipping a little bit more to my cabin steward the last evening....and sometimes the dining room waiters.
If the auto tips are reduced or removed, the employee who the tips would have gone to is called in by the purser to explain why, what they did wrong
, to have had their tips reduced/removed. SO unfair that they work SO hard for you, and then have to defend themselves when they know they did everything they could to please you.
do think long and hard before doing this.