i had a CFP in my fron porch last summer getting bright light for 4 hours a day and direct for mabey an hour or 2. I started noticing these discoloured spots appering on the leaves and thought there wre from pests ( after careful inspection i ruled this out). that brings me to now. I have a 6" ficus religiosa in a south facing window and noticed that it was also getting these same spots on them. unfortunalty i do not have a pic byt if you can post pics of some sunburntd or heat burned leaves it would help me out or confirm my guess thanks
it does sound like sunburn, you can prune off the damaged bits and move the plant to a less direct sun area, or put up some shear curtains to help filter the light.