Could you post a photo of the bud damage? If the buds are brown, that could be cold damage or petal blight (fungal disease), among other possibilities. If you're sure the petals have been eaten, that could be grasshoppers/other insects/squirrels?

It may depend on what part of the country you're in, which brings me to my strong recommendation that you contact your local county extension agency to get some advice about what is causing the problem. They should be able to give you geographically appropriate suggestions about how to take care of any of your plants.

Good luck!

Hi fleur i have several camellia sinensis plants. My plants have done this as they are very young right now they have the growing tip die off on a few. its almost certainly a fungus attack and a teaspoon of baking soda and water in a spray bottle will get ride of it. Make sure you spray under all the leaves with this mixture and give the soil a nice dampening with it. This will change the PH of the soil on the top couple inches and on the leaves. Makes sure the fungus can't grow. If you would like to tune into my Garden channel on youtube you can where i will have some more little tid bits on camellia and as well as some other food crops my channel is TheItalian Garden. hope this helped you if not ask me on my channel video How to grow camellia and i will see if i can assist you ferther.