Thanks for writing. It sounds more like a watering issue than too much sun. Stick your finger in the soil every once and a while and feel how moist it is. If it stays wet or saturated, then there's definitely too much water.
Are the leaves being affected throughout the plant or just on one side? If it's just on one side, it could be an environmental issue such as damage from hot or cold drafts or exposure to some sort of chemical (such as a cleaning product).
---Justin, Senior Garden Editor, BHG.com