Had they been ill or showing any symptoms? If ill, all could be sick. Had they been eating and drinking and if so, what? Babies need food and water available 24/7 - they eat non-stop. I also feed mine all sorts of good foods like shredded cheese, chopped up lettuce, veggies, fruits, and oats in addition to chick feed with vitamins in their water. I'm not an expert but I don't think it's "normal" for 2 seemingly healthy 2-week old baby chicks to be found dead - unless predator attack but it doesn't sound like that's what happened?
Watch the others closely for signs of illness.