inactive toddler ?

I have a 24 month daughter ..I am getting a little concerned these days ..she is talking well ..in sentences ..knows her rhymes ..numbers ..ABC ..etc..spends time in pretend play ..she started Montessori in Jan but has been on and off due to back to back sickness..she used to be high energy toddler running around ..doing summersault ..kicking ball..running in park..slides swings..when we used to be out she used to run and I had to chase her..but off late she wants to sit with us read book,puzzle or play kitchen set or lift her up..when I take her outside she will do little bit of slide and say let's go home..she walks also very slowly outside..I checked her in Montessori as well..when outside she is not playing with toys or anything just standing close to the teacher talking to her or standing and watching other kids..the teacher also mentioned that my dd just walks around and then comes to her and stands close to her..

inside the classroom she sits with everyone ..shares toys ..she talks about her classmates to me as well..

even with our frds kids she plays and does her five and hugs ..etc

she was not like this before I see this change in last couple of months when she started Montessori..she still cries at drop off and tells every morning she doesn't want to go to school..she want me around all the time ..she won't leave me and explore which is so odd..if I am brushing she will stand and watch me but leave me or do something else..she used to be so energetic ..why is she so dull and inactiveall of a sudden ?

Just to mention we always had either of our parents with us and then both of us went to India for 2 months ..so she has always been with lot of ppl and attention

We came back to US in Dec and she started Montessori in Jan ..this is her first winter as well