Camellia is in distress
This camellia is in a East facing foundation planting. Part of the plant is chlorotic and leaves look burned. It seems whatever is ailing the shrub is moving from one side to the other. The plant next to it is a cherry laurel. My guess after reading up is canker but I did not look it on the stems/trunk. The camellia is mature.
After the winter we had, many broadleaved evergreens are looking pretty poor. This is due to winterburn, which is damage caused by dessication, or drying out of leaves.
The underside of the leaf in your photo does not look concerning to us.
Unless there is great dieback, which doesn't look likely from your photo, as temps moderate, the damaged leaves will fall off and new fresh leaves should form.