How to know if daycare is the right fit

I’m a little at my wit’s end and a lot feeling like a terrible mom. We started our kiddo at daycare in January (she was 22 mo at the time). She showed all the signs of readiness: interest in other kids, emotional regulation at home/with nanny, participation in group classes like little gym and music. Her first few weeks were rough for the transition. She had some good weeks. Then we had her baby brother in late April and since then, she’s been hitting, kicking, not listening and not sharing. Without saying it directly her teachers told us she’s a problem child.

I’m heart broken. At home and in smaller situations, she’s a delight. Social, happy, sweet, loves reading. She has tantrums of course but she’s 2, it’s expected.

I know she’s in a transition period with baby brother, but it’s been 8 weeks. And she never had GREAT days at school, just good ones. When we pick her up she often seems lost/dazed. No smiling.

Should we start exploring different care? She’s really interested in learning letters and numbers so I thought about Montessori but she’s not potty trained yet.

Thank you to anyone for thoughts or advice.