Okay they need at least 85 with one end of brooder at that temp and other end cooler so they can get away from heat if they want. After their first week drop their temp 5* each week there after until they are at ambient temps.
Could little one have dust or feed In it’s eye? You can put little ACV into its water 1tea Ed quart of water you can rinse the eye out with saline wash which is 1/8 tea of salt to 1 cup warm water. There are products you can buy also Terramycin eye ointment. Veterycin makes an eye ointment. But...