We got 6 chicks at the end of April - 2 silver-laced wyandottes and 4 buff orpingtons. When they were 1 week old one of the wyandottes started gasping for air when we gave them grit. It seemed to go away but she died several days after this began. Now two weeks later the other wyandotte is dead. She was fine last night. This morning we found her dead. There was absolutely no warning. Now one of the buffs seems to be lethargic. The kids are heartbroken, but we don't know what to do. Should we give the lethargic buff electrolytes? antibiotics? Should we keep them extra warm? Both wyandottes were active, eating, having normal poop, etc. They really seemed like the strongest ones of the group. They live in a box in the garage lined with newsprint and papertowel. They spend the days in a cage outside where they have access to dirt, weeds, and bugs. We feed them chick feed and occasional treats like watermelon rind and moths. Their hatch date was 4/28, so they are about 3.5 weeks old. Any advice would be appreciated.