Baby not drinking or sleeping as normal?

So our little one is 6 months on Xmas day! For the last two days she’s only been drinking 3oz of formula and is showing very little interest in BF. She is also only napping like 20-30 minutes at a time.

She would put her self to sleep before this and nap up to 2 hours some days too. She was previously taking 6oz 4 times a day and then bf at night.

Does this sound like teething (no swollen gums or other signs of teeth) ? Or another sleep regression 😅