Looking at his Brooks page, with lots of grain of salt SSS caveats, I see a whole lot of "is basically never swung at and missed" on everything except the curve. If that's indicative of his pitches in general and not just a coincidental sample of his bad days then he needs another pitch with something more. Assuming it isn't just horribly obvious sequencing causing everything to get touched or crushed. His start in Tacoma isn't promising that the M's saw a sequencing issue and addressed it so I'm going to guess it's not that.
I never know if a mechanical tweak will make a pitch more effective and changing for one purpose can affect something else. Maybe his fastball gets better but his curve gets worse. I can only really speculate but even looking at overall stats it just seems his overall repertoire is just getting hit too much. There might be something to him getting too many strikes in that? It seems to me that another pitch being less hittable is his main current stumbling block though.