The chick is sick. But we can't tell you what's wrong from just the photo.
The most common cause of chicks acting sick is constipation. If you are giving treats to your chicks without offering chick grit, it's likely the problem. Give coconut oil chilled to a solid state and slipped into the beak until you get about a teaspoon into the sick chick.
Another possibility is coccidiosis if the chicks have been on natural soil for a week. Could that be a possibility? Also, check the feed for spoilage and dampness. The same for bedding that may have started to mold.