To me it looks like physical damage, maybe from the repot.
How big IS the pot? Watering every other day seems a bit frequent. If it dries out that fast it probably needs an even bigger pot.
Don't move it back and forth depending on temperature, Sunburn is dependent on light intensity not air temperature.
How much fertilizer do you use when you fertilize and how much does the package say to use? If the package says use 1 tablespoon and you use 1/2 a tablespoon, you're not getting the same response. On the other hand if you use 1 1/2 tablespoons you could be burning it.
