Aww, ganito talaga sometimes lalo na kung mix feeding kayo, ang babies nyo ay nakikita na na may easy alternative! Sa experience ng mga mom friends ko, nangyari din ito at natugunan namin by doing more skin-to-skin during the day, offering the breast first before the bottle, at ensuring na hindi sya overstuffed from formula kaya mas gutom sya maghahanap ng breast. Pero kasi nandito sya gumagana ng gabi, it could also be a phase or comfort preference, hindi pa naman alarming, pero I'd still suggest checking with your pedi or LC kung persistent pa rin after a week or two, just to rule out any latch issues or oversupply na nakakafrustrate sa kanya, okay? You're doing great with the mix feeding, mama, kaya don't stress too much!