this is a indoor garden
What Causes White Dusty Spots on the Top of My Plant Leaves
Certified GKH Gardening Expert
It could be water spots. If you water from above the plants, the water on the leaves can dry and leave a dusty residue which is the minerals in the water.
If the spots are more fuzzy like cotton, it could be mealybugs. This article will help you with those: https://www.gardeningknowhow.com/plant-problems/pests/mealybugs-white-residue-on-plants-leaves.htm