Ok, so Lilly's poo has been stinking pretty darn bad

for a while now. I think it started when I switched her over to Taste of Wild Pacific Stream. I'm talking like strong smelling make me puke poo. I don't know if it's her treats??? or her food??? or if it's something else. I give her peanut butter & apple Snausages and also the Yogurt Drops.
I don't know if I should switch her food as she actually eats it or if I should just deal with her poo stinking. She has also sniffed at her butt quite a bit lately and actually scooted it on my runner the other day

. Her stools aren't very firm like they used to be.
Any ideas?