You have been given good advice so far. I would not use ivermectin on the chicks. The chicks all appear normal to me in all of the videos. But in the last pictures, the watery eye and lethargic appearance might be pecking an eye, or the beginning of a respiratory infection. I would just keep the eye gently cleaned with a clean wet cloth and apply some antibiotic eye ointment twice a day. Then keep offering water and food.
