There are some very strong comments here which I can understand, but I thought it would be useful for you to hear from a former student who did a similar thing.
I passed my first year after re-sitting one module, but I struggled at the beginning of my second year and completely doubted myself. I was failing on a project and was supposed to be giving a presentation to all of my peers on my preparation and work so far. I didn't know anyone well enough on the course to go to for help and didn't approach my tutor either. My parents never attended college or uni and I didn't feel I could go to them so I panicked and after two weeks of thinking, I quit and got a job through an agency, thinking I could make enough money to prove to my parents that I could support myself. Of course, I could only get minimum wage jobs and couldn't make enough money.
After 2-3 months I had to admit defeat and tell my dad and stepmum. Dad was absolutely fuming of course and I had to move back home from the house share they'd paid rent for. I got a job straight away and they made me pay a monthly contribution towards the family home and suggested the best thing would be to take up a part time qualification at the local college whilst I worked.
I really really regret the whole situation and have to live with that for the rest of my life and explain it every time I apply for a job. It is just unfortunate that I wasn't mature enough for the responsibility at that time or confident enough to reach out for help.
Some posters here don't seem to believe your daughters' self esteem has suffered but based on my own experiences, I think it probably has.
I think given the length of time they've deceived you, it would be good to visit them in person to get to the bottom of what's happened to make sure there is not something else they're hiding. After that they should both get jobs and pay their way and try to find out what they really want to do with their lives. If you're not prepared to have them in your own home, then maybe they could get an apartment once they've saved a deposit.
The reason I owned up when I did was because I was essentially on my own and not responsible enough to take care of myself. Your daughters probably enabled each other with the deception and that is how it went on so much longer.