I have recently noticed a brownish film on bell pepper leaves and spots on others.
Brownish Leaves on Bell Pepper Plants
Certified GKH Gardening Expert
This could be due to some type of virus or fungus, often attributed from pests. Neem oil will help with any pest problem, as well as fungus. Here is more info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
This article can help pinpoint the issue: https://www.gardeningknowhow.com/edible/vegetables/pepper/pepper-problems.htm