You don't say, but I'd guess these were container plants that you bought and planted?
This sounds like problems typically associated with rootbound plants, and possibly planted too deep related to the trunk/root flare of the plant.
Since you have 3 of these plants, dig up the poorest performing one and examine this situation. Take pictures, and post them here for analysis. If I'm right, you'll see the primary roots still growing around the soilless media that was in the container. Also, check where the roots flare out from the base of the trunk compared to what the current soil level at which this shrub is planted.
Rootbound/circling roots will be obvious - likely still growing in the zone of the container media. To resolve this, you need to loosen and spread these roots out in the site you are planting them in, so that there is good root/soil contact and relief from the circling pattern created during container growth. This requires disturbance of the rootball in order to separate and tease out the roots to grow radially instead of circumferentially. Hopefully, you have granular garden soil to settle back in around these roots when you replant.
Planting height is also critical, whether you have a perfect or imperfect root situation. Planting too deep is often the cause of poor performance and ultimate failure of many plants. Examine where the branches/trunk descend into the soil. The planted soil line should line up with where trunk becomes the root flare, NO MATTER HOW THIS WAS GROWING WHEN YOU BOUGHT IT.
This is the Caveat Emptor moment.
Replant your shrub with this base of trunk (root flare) at or slightly above the finished soil line in the planting site. DO NOT pile mulch up against or over the branches and trunk, as this can promote problems with pathogens.
Please post images if you dig one of these Camellias. It will help others here to assess your situation better, and provide information/object lessons to others to help everyone have more success with their plantings.
