It really is an injustice when a plant is grown in perfect greenhouse c-onditions that mimics only the best tropical warm, humid areas, and then expected to do well in the average home humidity. They usually don't, needing an adjustment period often a month or longer. It is distressing to say the least. I hope your plant comes back to you, Basil. Baby it and spoil it for a time and I bet it will. But yes, watch the over watering. We sometimes tend to over love our new plants to the point of drowning them.