8 month twins still waking up 2+ times overnight

My twins have slept in their own (shared) room and gone down for the night without issue since 4 months. We had 2 months of them sleeping 7 pm - 4 am, then a quick bottle and back down until around 6, which worked for our family.

Since they turned 6 months, they have been waking up at 10 or 11 pm, again at 2 or 3, and up for the day at 6. My husband and I are so tired, and most of the advice I’m finding online is about sleep training for the beginning of the night, which isn’t a problem for us.

We do give them a small (2 or 3 oz) bottle every time they get up, and we wake the other twin if only one is crying to avoid adding even more rounds.

I’m not opposed to CIO, it’s what we did for naps and the beginning of the night. Should I just plan for a long night and try CIO for the first wake up?

Schedule is around 3/3.5/4 but we mostly shoot for by the clock at 9 am and 2 pm, 90 mins each nap. Bedtime at 7. Bath at 6 and calm playing/hanging out/reading until bed.