Toddler habits? How to get rid

I posted last week about my twin girls last week and got some good advice so wanted to post here on different topic. They’ve recently picked up some habits that I am not sure how to handle, for example spitting? They’ll constantly spit on the floor, on the high chair and play with it, will spit in their hands and spread it all over their face. They’ve also discovered pinching, particularly one of them who’s bullying the other by pinching her constantly. Hitting/slapping - again this is towards everyone. They’ve discovered no and they actually mean no, so when I ask for an apology, they’ll say no. One of them has started grinding her teeth(???) Not sure how to handle all this. I tried redirecting their attention with stickers, singing and/or toys but it’s exhausting doing this ALL the time bcos if one starts to spit, the other quickly follows her and now I’m telling both of them off. Help me please!!!