Hello Andrew,
I can see this is your first post. As a piece of advise you would get more feedback if you can post the music or the part of the music that you are referring to so those without, or that are not familiar with the piece can easily have a look and assist you with this issue.
I have listened to a few pieces and it seems that they play 2 graces notes either side of the 3rd triplet as evidenced in the performance below. Due to them being triplets, I don't think it's exactly in between the 2 notes it seems that the 3rd note of the triplet comes promptly after the 2nd grace note which slurs over the triplet and adds the following 2 grace notes.
I think you can be free with that though I just think that it shouldn't be played in time, together due to the triplets.
Sounds quite nice so I hope when things are ready you'll post your playing in the Audition forum.
Maybe practice first without slowing down so you can work out how to keep the triplets in time with the added graces notes then slow it down when you're definitely sure of the notes' timing.