Camellia buds turning brown and when buds open the flower petals fall off the plant. Why? Buds are multiple at each sight on the branch. When one opens, the flower petals fall off of the branch. In other locations, the buds turn brown. Plant is in very shaded area.
Camellia Buds Turning Brown
Certified GKH Gardening Expert
Based on the symptoms, I think you should check for the presence of bud mites, which can only be seen with a magnifying glass. If you detect mites, you should spray them directly with either horticultural oils or insecticidal soaps.
If you do not detect mites, then the bud drop could be due to over or under watering or a drastic change in temperature. These reasons and others are fully explained in the following article;