Are you using Warm and Natural (or warm and white) batting? If so your batting is on upside down. This happened to me once. I use the rhyme "bump up" to remind me. You can cut the batting that isn't quilted yet and flip it over which is what I did, but my rack (Innova) is very easy to do that because my roller for the top lifts up for easy access to the batting.
If you using your Sweet16 as a sit down and used spray adhesive.... Well, I don't have an easy answer for you.
There is nothing that can be done for the part that is already quilted. Live with it or pick it out. But for the rest of the quilt you can cut the batting flip it over and butt it up right next to the batting that has already been quilted. It won't show once the quilt is all qulted.
Edited to add, your thread choice is what dictates what needle to use, NOT the batting.
To the other posters, she would not be able to use a DSM needle in the Sweet 16 as it would not fit and is not long enough. She wouldn't even be able to stitch with DSM needle
I prefer Groz Beckert needles for longarming. You can buy them on line or from your dealer I am sure. Go here to learn which needles to use with which threads:
http://www.superiorthreads.com/reference-guides/
Click the link that says "Longarm Machines Thread Reference Guide"
Here is another great education link from Superior
http://www.superiorthreads.com/educa...-needle-codes/