Daycare changing terms after signing agreement

Location: MD

I just received an addendum for my daycare in which they are now requiring a 1 month tuition reserve for the 2025/2026 school year and are asking us all for $1,500 each to hold in case there are any gaps in payments etc.

Signed tuition agreements and re-registration fee payments were due in in April.

What’s the legality of making such sudden mid year changes? We’ve used this place for almost a decade with all of our children and never seen anything like this