You should never multiple people on the same Apple ID. Use Family Sharing to manage the new Apple IDs. Add your Apple ID to it, and the newly created ones that you've made for your daughters. https://support.apple.com/en-gb/HT204316 https://www.apple.com/family-sharing/ The reason they are getting the same messages is because Messages (regardless of whether iMessages or not) synchronises messages and calls, are synced between apple devices (eg; I can take a call on my mac).
It lets you share app purchases and subscriptions, but keeps personal data private. If the reason you had the same Apple ID was parental controls, just use 'Screen Time' to set limits, and 'Ask to buy' to stop them from overusing their devices, but more importantly, the latter stops them from buying or even downloading free apps without your permission [It sends a notification to your device, which you can open, and shows you the info about the app and lets you accept and decline the purchase / download].