Jennings is pressing. He's 'trying' instead of just playing football. He's choking, plain and simple. All the guys that seldom get targets will do this. It's human nature. Tannehill only has eyes for Landry. The others are just running for exercise. If this continues, you're wasting everybody.
Get Jennings some targets, he'll catch a couple and then he'll go back to being a good football player. Or, just cut him. Seriously. 2015 is over, from a playoff contention standpoint. Might as well serve the youth.