Potty-training multiple children tips and tricks? Please help me!

I run a home daycare and have 5 children in various stages of potty-training.

One of them is almost 4 and previously was completely potty-trained but regressed when a girl his age started attending who was unpotty-trained. He still pees in the potty but has pooped his pants ever since.

I have a two and a half year old who goes pee some of the time but has constipation issues and tries to hold it in and ends up having accidents of both kinds.

I have a three year old that will start attending on Monday along with two complete unpotty-trained two year olds. I’ve been told the three year old goes pee but not poop in the potty.

If you’ve made it this far thank you! I’m new to this and so far no methods I’ve tried have been successful so open to suggestions about each individual child’s situation or potty-training a group of children in general. Please also include if you are a parent and/or work in childcare, just curious but all advice welcome