General Fitness

The typical 3wks on, 1wk de-load applies.
You just need to have it stored (either on paper or in your head) on what they can individually do.
eg - Push ups, we do on high bars for beginners, and then progress to medium bars, then low bars then flat ground etc.
Squats might be Box squats for beginners, then holding onto a med ball, then free squats then jump squats maybe etc.

i can have a good sized group all doing the same thing, but each person within that group is doing each exercise slightly different

I know a lot of trainers who simply cannot do that. I just prefer it.