leaks from upstairs

Those stains are on my ceiling right below my bath tub upstairs. In your experience, what is the likely cause for this?

Where do I even start! We live in a two story home with a seldom used upstairs jack and Jill bath with toilet and shower that was recently cleaned. We also have have a standard hot water tank with recirculating pump for hot water. I have been out of town but my husband called one morning and...