At her age, the first thing I would do is give Corid in the water, just in case of coccidiosis. She is on the younger side if it is Mareks. But chicks with Mareks may have problems with immunity fighting off common infections. Time will tell if it is Mareks. Look for any signs of lameness in one leg or drooping wings, and imbalance. One type of Mareks can cause eye color to fade and the pupil shape to change. Make sure that she can reach food and water. If you use Corid, dosage is 2 tsp of Corid liquid per gallon of water for 5-7 days. The dosage for the Corid powder is 1.5 tsp per gallon.