It does look fungal. Maybe powdery mildew? Many fungal diseases are result of environmental problems. Most of them spread and spores could be 'hiding', so just trimming some visibly infected leaves usually doesn't solve the problem.

Maybe you need to change something - you didn't say anything about growing conditions (watering; potting mix and container; light exposure; temperatures and where it is growing...) Plat should bounce back once conditions are improved.