Kidney cleanse herbs : harder stools?

I am using a herbal mixture for kidney cleanse. The mixture has the following herbs. Somehow my stools have become harder after starting using it. Could any of these herbs could make stools harder? Or it might just be a coincidence and there could be other cause? I drink a lot of water, and taking lower bowel balance capsules also for the bowel movement and they work well to not make me constipated.

Chanca Piedra
Hydrangea root
Marshmallow root
Stinging neetle leaf
Plantain leaf
Uva Ursi Leaf
Gravel Root
Corn silk
Comfrey
Dandelion Leaf