No, they almost never cover all four events in a single practice. One apparatus will get a significant share of the time (like 2 hours), and a second gets a smaller cut. Sometimes they finish up on a third, but it'd be pretty focused--working flight skills on beam for the last 20 minutes for instance. However, no apparatus gets slighted. If Monday is "big bars" day, then Tuesday is "floor" day.
Chances are, every athlete in they gym has an event she'll struggle with. It might not be so noticable at level 5, but will become more obvious as you watch those girls who continue with the sport.
Your last question is kind of hard to answer because even girls who are excelling are paying for and deserve equal attention from the coach, even if they're perfecting rather than learning. And there can be resentment if it appears the coach spends all her vault time, for example, with one or two kids. "Helping" the struggler can only be done to the point where the other girls aren't cheated out of training.
What I used to see was that the coach would be standing next to dd2 on the beam (cuz dd2 had the worst BWOs--BT, no problem, but those walkovers were awful) so she could give her more spots, and calling out corrections to the other girls. However, she could only stay near dd2 for so long. Bars were more difficult. We had a lvl 7 who never did get her giant, but the coach needed to be closer to the girls doing release moves for safety reasons, and couldn't spend the majority of bar time close the struggling 7. In those instances, when a skill or apparatus was really an issue, it was an option for the parent to schedule and pay for a private. If it's summer time, camps might also be an option.
Sorry if that wasn't very helpful.