If it was in essentially full sun all summer and you only watered it "every couple of weeks" when it didn't rain the problem isn't too much water, it was under-watered all summer. When I worked in nurseries we watered almost every day (we never had that 'rain' stuff). For a plant that big in that size pot, I would give it a good soak at least once a week if temps are 80 or above and it doesn't rain.
Sally's question about how long it's been in that pot is a great one. If it's brand new, then it can go longer between watering. If it's been in that pot several years, it will need more water until the leaves fall off (which they will). If it's in that window and getting supplemental lighting, once every 2 weeks would be about right. Of course, a deep probe before you water will let you know if it really needs it.
