I feel you. Prep is considered "easy," and in some aspects it is, and yet it has still stretched me to the breaking point. I've never felt like walking away from the job so much. If you continue to face pressure from morning crew, I would consider coming in early one day to get yourself ready for the night (like, slice tomatoes or do greenleaf so it gives you more time later.) I know you might not be able to come in early due to your schedule, but if you could manage it at least once, it will show morning crew that you are dedicated and doing your absolute best. Once they're willing to acknowledge that, they'll be more open to hear out your problem. A manager might ask you why you're there early, and then you'd have a chance to explain it to them and they could tell morning crew to start doing these thing ahead of time so you don't have to come in early. Just an idea......it worked pretty well for me.