Amir Coffey's shot got drastically worse his senior year (largely because he was forced to play PG). He shot 30% from 3 his JR season (37% his SO season).

King and Mason's numbers slightly decreased.

Oturu did get better.

I'm not sure what numbers you're looking at but True Shooting Percentage is the best measure of a player's shooting because that encompasses all types of shooting (2s, 3s, and free throws) and weights those accordingly. Joey King was quite a good shooter here and his TS% was remarkably stable over his three year career at MN: .600, .608, .605 for soph, jr, and senior years respectively.

Mason's corresponding numbers for his four years were: .504, .493, .494, and .526. So, Mason was never a particularly good shooter here but the senior mark clearly was his best.

Coffey's corresponding numbers were: .559, .566, and .537. He was a good, but not great, shooter and you are correct that his last year was the lowest of the three.

Oturu was good as a freshman (.568) and even better as a soph (.612) so, yes, he improved significantly in that measure.

To put these numbers in perspective, the top marks in the Big Ten this year were:

1. Kofi Cockburn: .637

2. Hunter Dickinson: .628

3. Luka Garza: .620

4. Joe Weiskamp: .616

5. Donta Scott: .615