Washington's effectiveness in the air and after the catch makes him an enticing NFL draft prospect.
Mitchell is the second cornerback to join the class.
Cottrell has committed to Penn State after earning a preferred walk-on offer in January.
The two seniors' reported decisions to enter the transfer portal come less than a week after the Nittany Lions' elimination from the NCAA Tournament.
Brown is the second member of the Class of 2022 to announce his intent to transfer.
Although Penn State's season ended in heartbreak, the program is primed to continue its success.