Your photos seem to indicate that the plants are chlorotic (yellowing leaves with green veins). Chlorosis generally is a result of soil that is either alkaline or barely neutral.

To correct the condition, feed with chelated iron or a fertilizer that is formulated for acid-loving plants (camellias, azaleas, rhododendrons etc). The plants are stressed, so be careful not to overdo the fertilizer. If the plants respond, you might consider amending the soil by carefully working in some garden sulfur around the roots. The sulfur will adjust (raise) the soil pH. Working in a top dressing of cottonseed meal once a year will also help.

There are other possibilities include that your small camellia plants might have too much of sunlight and the root is not yet established with the ground.

I agree with jaxondel. It does look like an iron problem. Check your soil moisture level as well as the pH. According to Ortho, minor nutrients such as iron are found in most soils, but soils with a high pH or wet soils prevent the plant from absorbing the nutrients. Camellias like an acid soil in the 6.5 range. They also like to be moist, but not wet and well drained.