I'm navigating this same thing myself right now and have just used a lot of trial and error. I have thought about making a piece of paper/notecard for each girl on each event, but ultimately figured that would be too complicated with them getting lost, forgotten, confused, etc. Maybe later down the road we will give it a try. I do something similar to what WSCoachLY suggested.
Bars is somewhat easy for us- I base what each child does on the spotted station where I am on where they are currently. So while some kids might get stuck on routines or skills in the routine, the kids who have proven themselves proficient get to move on. Side stations (we usually only have 1 set of bars) are largely strength and body shapes, so they all do the same.
Beam I will usually give progressive assignments and how far they get depends on where they are with the skill. For example, they will have to make 5 of their acro skill (cw or hs) on a line, when that is complete, they can move to a low beam. They keep moving up until they get to a high beam (or wherever they get stuck). The kids who have the skill reliably work through it quickly and get to move on to the next thing (their 2nd acro skill) while the other girls get a little extra attention wherever they seem to be stuck or pulled aside for drills. I do something similar with jumps and turns, though they usually just start on a low or middle beam for these. Girls who quickly work through the skill in their routine (1/2 turn or tuck jump for example) are allowed to move on to the next step.
Floor they all essentially do the same leaps, turns, and jumps, so not much variety there. Just a mix of drills with the actual skill. When it comes to tumbling they are all over the place, so I will set up a drill station along with a spotted station that I change based on the girl- some are doing spotted standing bhs while others know to do unspotted ro-bhs when they get to me.
For conditioning or strength side stations, I have certain milestones set for them. When they reach that milestone, they get a sticker on a chart and get to move on to the next step. So once they have 5 unassisted leg lifts, they "get" to work for 10. Once they have a standing press hs against a mat they get to move to the floor. You have to carefully word it though so it feels like a big achievement rather than some kind of punishment for getting stronger
.