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It sounds like you have thrips. This article will help: https://www.gardeningknowhow.com/plant-problems/pests/insects/controlling-thrips.htm

This sounds like a job for the Extension Service. This is a service run by your state dept of agriculture (and paid for by your tax dollars,) that offers free analysis of plant problems and advice on all things growing. This link will help you find one close to you: https://www.gardeningknowhow.com/extension-search/
Call them first to see what they recommend; usually they'll want to see leaf, flower, and soil samples.

It sounds like the camellia may have root rot. This article will help: https://www.gardeningknowhow.com/plant-problems/disease/treating-root-rot-gardening-tips-for-housplants.htm Treat the swiss cheese plant with neem oil. It is safe for people and pets and will treat both pests and fungus. Here is more information: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm

I would add phosphorus to the soil. A lack of phosphorus will cause a lack of blooms.

I would only prune it back by 1/3. You can follow up next year with a pruning of 1/3 again. Any more than 1/3 and most plants start to have problems. The following article should help as well: https://www.gardeningknowhow.com/ornamental/flowers/camellia/pruning-camellias-how-to-prune-a-camellia-plant.htm

You could try giving plants a teaspoon of Epsom salt (per height of plant if using on shrubs like camellia) dissolved in water (ratio 1 tsp Epsom salt to 1 qt water). This article should help: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/epsom-salt-gardening.htm