I would just say "ewwww that's yucky!" or something to where you aren't fussing but you arent like being positive about it either. Lucky :/ mine apparently goes at school but refuses to go at home 99% of the time
Charlee did the same thing, I just basically started back over (in a sense) took her potty every 15 minutes or so, told her that big girls don't potty in their panties and she is a big girl now etc