Vet career - what am I missing?

I'm running a clinic with two of my household Sims because employees were a huge headache... I'm stuck at 4 stars and it says that I need to improve quality of service. I'm a bit confused about how I'm going to do that considering that both my vets are level 10, always diagnose pets properly on the table, I always give them whatever shot is appropriate (or take them to the surgery station if shots won't do it), and I have high quality supplies. I have all the useful perks at this point too.

Any input? Am I doing something wrong? The other thing that can improve is ambiance, so I suppose I could buy another vacuum or two and have three of them run instead of just one (I clean up as fast as possible, but yeah, sometimes it's still too slow).

Also, diagnosing a pet makes no sense whatsoever because my Sims somehow figure out that my dogs have low temperature by checking their mouth.

Moving on...

I hit a bug as well where a pet at some new illness but the only option I had was to give him a preventive shot... but it only happened once.

The crafting station - is there any point at all in making anything else than treats with it?

Overall, I played it enough to get my Sim the wealthy aspiration (it didn't take long, at 5000 Simoleon earned a day, then transferring money to their account), but it's boring and repetitive and I'm not really seeing much point to keep playing it.

Just wondering what everyone's opinion is about this.