During Summer it could be dehydration, During Winter it might be because of the cold.
A couple recommendation are:
1. Avoid tap water unless you have a water filter at home. Tap water contains several minerals and chemical compounds. These ingredients are harmful to plant health, and well-being. Sodium and chloride compounds could be the cause of the leaves turning brown/black after watering. These chemical compounds are toxic to the plant.
So it's best to use room temperature filtered water, or you could also collect rainwater.
2. During Summer: Water it every ten days to avoid dehydration. The best way to go is by the weight of the ball, the lighter it is the most water is going to need.
3.During Winter: Water it every twenty days to avoid overwatering. The best way to go is by the weight of the ball, the lighter it is the most water is going to need.