Dropping ounces

Is anyone else’s LO dropping ounces from their daily feeding? I exclusively pumped until my daughter was 7 months old when I had enough in the freezer to last her until a year. While I was pumping I rotated my stash and she got frozen milk one day per week. She has steadily drank 24-26 oz per day since she was about a month old but the past few days she’s struggling to drink 18-20 oz and the bottles take forever for her to drink. I tried switching from a slow flow to medium nipple today but it didn’t really help. Some bottles she is done after an ounce or two and just wants to go play or stand. I keep offering her the bottle every few minutes and she will drink part of an ounce and then throw the bottle again. I don’t know if it has to do with teething since she has been extra fussy and drooly too, or if she is just more interested in solids. I’m just concerned about her getting enough and really not loving seeing all the milk I worked so hard to pump go down the drain.