Hello, wodka. The yellow leaf color could be one of several things.

1. If the leaves are all yellowed out but the leaf veins remain dark green, your plants are suffering from lack of iron. But if the leaf veins have also yellowed out then this is not the problem; read #2.

A fix for Iron Chlorosis requires that the soil Ph be lowered into an acidic range near or below 7.0. Short-term solutions include adding lots of organic compost and buying liquid iron chelated chemicals to help acidify the soil. Your local nurseries should have lots of these. You can also ammend with Soil Sulphur, Garden Sulphur, etc; just follow label directions.

New houses often leach lime from cement and this lowers the Ph, specially within a few feet of the house.

2. Check to see if the plants were planted slightly higher the surrounding soil. When planted below the surrounding soil, the surface roots cannot breathe very well. About one inch above ground is ideal.

3. If the soil around the plants has been kept wet, the plants could have developed root rot, a fungal infection of the roots. Root rot kills the roots and this makes the top of the plant unable to get water. The leaves then yellow out and die. The rest of the plant dies afterwards.

4. Insufficient soil moisture can also cause full yellowing of leaves in a similar manner as root rot does. It is actually very difficult to tell them apart unless you lift the plant from its hole and visually check the roots.

Your best approach here is to try and maintain constant soil moisture. About 3-4 inches of acidic mulch will help. You also need to water only when the soil is almost dry or dry. A manual technique can assist. Insert a finger to a depth of 4 inches and determine how the soil feels: wet, moist or dry. If it feels wet then you have too much water in the soil (which is ok if it recently rained or the sprinkler went off). Water only when the soil feels dry or almost dry. Notice the watering pattern after a week and set the sprinkler accordingly. If you are watering every three days, set the sprinkler to water every three days, etc. Provide the plant with about 1 gallon of water with every watering. Re-check manually when the temperatures change (up or down 10-15 degrees and stay there) and adjust as the plant gets older.

5. Bud drop can also be caused by the weather or pests (such as camellia bud mite or squirrels). It is very common for newly planted camellias to loose the buds on their first season. Wild temperature swings can cause also cause bud drop. To reduce the change of bud drop further, stop fertilizing around August and be careful when using insecticides that cause bud drop near camellias.

Does that help you?
Luis

Here is a link that might be useful: American Camellia Society Website