Cattleya seedling - sun burn or fungi?

[Jasper]

My cattleya Morning Glory hybrid seedling, has developed this brownish spot on one of her leaf. It wasn't there 3 days ago. Took pictures from front/back and shade/in sun. Am not sure if it is a form of sun spot/burn or a fungus infection.

Still a seedling so only a couple of leaves. If it is fungi will have to cut, but if ok want to leave her be
Appreciate comments of maestros.

With my home very shady I put my seedlings under direct morning sun for about 1 - 2 hours then bring it behind a shading for the rest of the day outside. When forecast calls for temperature going over 90s they are brought inside and sit by the south window (bright but no direct sun hits it)