How do droppings look? At 12 weeks I'd be more inclined to suspect coccidiosis. Most common symptoms are lethargy, sitting fluffed up, going off feed & water, runny, mucousy or bloody droppings. Not every strain will show blood in the droppings.
I'm very weak in knowledge of what you can and cannot get in Canada, normally we treat with amprolium, I believe the brand in Canada is Amprol. We can get over the counter here, I think you have to get from a vet, I'm not sure. This thread from June has one poster in it suggesting scours tablets, see post #20 & 21 for medication suggestions if a vet is not an option:
https://www.backyardchickens.com/threads/bloody-chick-poo-pic-included.1254831/page-3
Here is a link on Amprol:
https://www.drugs.com/vet/amprol-9-6-solution-can.html