Depth issue

I have this mc, its a bigger version of my footer that i made, except it has a border, the problem is, some times the bubbles end up above the border.
To duplicate the bubble MC i used:

for (i=2; i<numBubbles; i++){
	bubbles.duplicateMovieClip("bubbles" add i, i+100);

where i+100 is the depth, no matter what i set the depth too, the bubbles still seem to end up on top, i’m not sure what to do…anyone know?
heres the .fla…