sick again

The girls all have mild colds...again. I really think I'm cursed. It seems like they're sick at least as often as they are well and it's making me paranoid. What am I doing wrong??? I feed them vegetables, but maybe not enough. They wash their little hands after we get home from the store, after they come in from playing outside, after they go to the bathroom, and after we get home from church. Don't tell me it's too clean in here. It's not. I haven't done deep cleaning in over a year. Maybe that's the problem. I need to wipe the baseboards, clean the windows, wipe out the kitchen cupboards, and wash walls. I don't know but I wish I did. I am so sick of sick kids.