It is hard to diagnose correctly over the Internet. You may have one of many problems. Here are a few things to consider.

I would start by investigating insufficient trace minerals in the potting mix. You can add some liquid seaweed or liquid fish, products that contain these trace minerals. Then observe the plant for changes (does the problem stop, for example).

This is also the time when some camellias drop old leaves so maybe what you see is related to old leaves dropping off.

You can also locate the shrub where it gets some early morning sun. A couple of hours is all you probably need. Bright indirect light helps too.

It could also be a fungal infection called leaf gall but it is rare on C. japonicas so you need to confirm before taking action. The leaves get swollen, thick and large looking. It does not damage older leaves and twigs or other plants so many people do not apply fungicides. The gall that appears can be cut off before it dries out in a few weeks. Apply something on the wound to prevent other things (dieback fungus, etc) from entering through the injury. Better yet is to prune the affected area. This is a common problem in rainy locations so good drainage and morning sun (2-3 hours) may help keep fungal infections at bay. Replace the mulch with new mulch in case it harbors spores. Make sure the potting mix does not stay wet.

ionah, camellias do best in the outdoor environment, not inside. I suspect that that is one of the problems.

We also don't know what kind of potting mix you are using. Young rooted cuttings do best in small containers filled with a very coarse, bark based medium. Regular potting soils are not usually porous enough. Also, I worry that by keep it 'moist', the soil might be TOO moist. That will absolutely cause root rot rather quickly.

What happens when a container plant suffers from root rot? They wilt and drop their leaves.

I tend to think that if it did not droop until you potted it, that could be the problem. Several things to keep in mind with camellias. They droop because of stress - figuring out what stress is usually the problem.

The first thing I'd do is check the planting level. Camellias are shallow rooted and planting too deep in a container will starve the roots of oxygen. If you combine this with the use of a commercial potting mix - you could be compounding the problem - because CPM's usually contain a lot of peat moss that holds a lot of water. Watering is good, but if the plant is waterlogged - meaning that the majority of what you put it is not coming out - then it's too wet.

You can amend bagged potting mixes with with perlite to improve drainage. I have successfully used 1/2 potting mix and 1/2 perlite and they have done very well in containers.
You will have to look at the watering because the pots will drain very well - which if you're not watching out - they could dry out. But you can add water - you can't take it out!

I'd try to get the drooping plant out of the condition it's in. Rinse off any of the old soil- but don't completely bare root it. Repot it it in 1/2 potting mix (or bark if you can get it) and 1/2 perlite. Keep the roots near the top of the surface, but not exposed. Water well and make sure it drains. I'd try to use a transplant fertilizer - like Miracle grow liquid - they make one - it could help the plant get over the stress. Also don't use saucers - they have a wicking action.