Our starting 9 are all mechanically sound. 4 going on to college. I've seen a lot of kids that are "hitters", but struggle with slow pitching. The whole reason to be on plane is in case your timing is off a hair. With arced pitches, you have to be puntual to the ball. Being on plane doesn't help much. I almost want to tell them to top it so they wait for the ball to come off the arc a little.
I kept this varsity team together last year for travel and all we saw was good pitching, now at the high school level we don't have that 80+ fb everyday. The kid that thru 88 just came off his last game of 19 Ks, but we slugged 10 hits off of him.
Sounds like he was throwing too many FB and maybe left too many up. Having a good change up matters. Your team sounds like they r better hitters. 19 K was prob against a team that couldn't hit an 80 FB.
We just had local team here who pitched their college bound P against a school that barely can field a team. Ridicules, guess coach wanted to get him another W, when he could have used a lesser pitcher who needs mound time and still won.