floom. I don't grow geraniums but I will take a stab at your problem.
Picture in your mind how this plant was grown from seed, commercially. It was most probably grown in completely controlled conditions, in a huge greenhouse, and in bright light but not sun. When the plant was ready to sell, it was jammed into trays/flats, transported from who-knows-where to who-knows-where. They it was probably shelved in a warehouse/distribution center until it was shipped out again by truck to your grocery store. It then sat in your grocery store for a period. All this time, from the greenhouse to the grocery store, it had no light and probably no water.
It is now a highly stressed plant. Perhaps when you got it and read about its care, you began to water it, fertilize it, and let it get some sun..........six hours of sun. Because the roots were stressed along with the plant, those roots couldn't do much about taking up that water and certainly couldn't utilize that fertilizer. The leaves have had absolutely no sun their entire life and now the sun is beaming down on them.
My guess is that the plant needs shade, not sun, needs no fertilizer until you see active and healthy growth (and even then, I would use a water-soluble fertilizer at 1/2 recommended strength), and only needs watering when the soil is dry at least an inch deep. Misting those traumatized leaves twice a day will not only raise the humidity but also help to hydrate those desiccated leaves. As with fertilizing, you can gradually introduce the plant to sun when you see that healthy, sustained growth.
That's the best I can do. I have over 1000 tropical plants and this is what I do when I get plants in from commercial growers. I am sure there are lots of folks that grow these plants and can tell you more than I have.