Overfilled my coolant reservoir?

I had gone on a trip. Car was fine. When leaving to come home, I mistakenly added too much WATER to the reservoir. The whole trip until now, the low coolant light flickers on and off. I drained the reservoir, replaced it with the correct amount of coolant. Radiator was fine, lost no water and when tested only one ball didn't float. I do think that the car is heating up more also but not sure since the weather is so hot. I would not recommend overfilling your reservoir ever.