It may be nothing to worry about, however, just in case...
At 5 weeks, you should watch for signs of coccidiosis, which is very common. Symptoms are runny, mucousy or bloody droppings (blood is not always present), lethargy, sitting fluffed up, going off food or water. If any look off, or if you see any of those symptoms I would start treament for coccidiosis right away. Treatment is Corid, available at most
tractor supply stores or feed stores, usually in the livestock or cattle area. Comes in liquid or powder form, either will work, but most prefer the liquid for convenience. Dosing is 1.5 teaspoons of the powder or 2 teaspoons of the liquid mixed in a gallon of drinking water. (the dosing on the package is for cattle, not chickens). The medicated water needs to be the only water they have access to, no puddles, ponds, streams etc. Make fresh daily and treat for 5- 7 days. Images of the products below. If you suspect that may be what it is, start asap, the sooner treatment starts the better chance they have to recover. I would treat them all even if only one had symptoms. Corid is very safe.