I didn't know they could be withered after watering! On the other hand, if you hadn't watered them, they would be gone, so withered is a definite improvement. I think this is a change from previous games though. I'm pretty sure if you watered everything you would not have any withered flowers the next day. You could keep your flowers beautiful by watering every day. Seems you should have this option if you are willing to put in that kind of work!