Why are my baby mice afraid of me all of a sudden?

I'm a having a little bit of difficulty with my pet mice. Six days ago I found 4 orphaned baby mice. They looked as if they were only 2 weeks old and their eyes were barely open. After much time, effort and money, I nursed them back to health.They are beautiful and healthy now. Now the problem is that when I was feeding them formula every few hours, they would all come to my hand immediately. They would spend one-on-one time with me while I fed them and make the clicking sound constantly. Now, in the last 3 days, they are feeding on their own and are completely scared of me. They no longer come to my hand or to the sound of my voice. They hide in their tube the whole time i'm there. And they sleep a lot. I'm just worried that I've lost their trust and I'm not going to be able to tame and bond with them. I've been trying treats and leaving my hand in the cage for periods of time but they won't even flinch. What would you recommend I do? Please help!!