So what are the parents' responses when you bring up these issues? If you haven't yet, you MUST immediately. Give them a chance to fix the problems, but if they don't/can't/aren't willing, terminate.
Do you want the rest of the kids in they daycare picking up these habits? I am thinking no.... and it's not fair that they have to live in fear of being picked on or spit at (Yes, to me that is spitting "at" you, even if it's not a big loogie-spit).
Develop a specific action plan, as others have said. Include what the consequences of the behaviour will be and if mom/dad aren't on board, I say you need to be done!!!
**HUGS**