I came from a bad childhood. I won't go into detail but I can say when kids feel threatened or told firmly not to do things they do two things. 1) they do them, because they want attention (I was that kind LOL) or 2) they don't do it because they are scared of what might happen.
The only thing you can do is love them. Its that simple. Of course you should sit down with them (like above comments) and reassure them that if they're sick they're not going to get into trouble and just come to you. It will get better with time but they need trust. If they can trust and love you, they'll come to you.
The reason why they get each other to come and ask questions for them is that you won't get mad at the person asking, and they feel safer that way. Don't get angry when they do it, just next time they do it go over to them, and sit down with them (AT EYE LEVEL) and talk to them in a calm voice. Yelling can do numerous things a child, from making them insecure or reflecting it on their peers.