Pretty much this.
He hasn't finished as strong as he was last year and it comes down to two things. Mental approach and putting. He lead the field in putting when he was winning match after match, he also never gave away shots when he was coming down the stretch.
The kid's still playing phenomenal but it seems that people have become a bit desensitized to how hard it actually is to win a PGA event in 2016. He doesn't look as confident in his swing at the moment, body language can tel us that, but to be leading events on Friday/Saturday with your B game is still impressive.
Spieth will be fine. I'm just a little tired of seeing the golf critics critique a swing that is almost identical to the one they claimed to be perfect a year ago.