He has a massive uppercut and long swing. You can pretty much say that about almost every hitter on the team
They are probably too far gone to change. Same as hiura.
I would start with something basic for hiura for example. Try to hit the top half of the ball every time. Same with Adames. See if that helps make more contact then go from thete
yelich is just not even worth trying to fix. Personally I think he needs to spend the off season with a rigorous weight training program.