Discoloration under doming resin

I have been asked to do a necklace using the Colores Doming Resin.
The necklace has 18 seperate bezel cups attached by JR’s. I am having
trouble with spots of discoloration under some of the pictures. It
doesn’t show up until after I put the Doming Resin on top.

The sample video Rio has on their website suggests using a “white
glue” to adhere the photo to the pendant. Also to put the white glue
on top of the photo to seal the photo. I did that using Mod Podge
white glue. At least I thought I sealed them. The spots are sometimes
on the edge and can also be in the middle, not touching the edge.

Could these be air bubbles trapped under the photo? I am at a loss. I
hope someone can help me. Thanks so much for any advice.

Kirsten Reynolds