Because your Camellia is in a container and watered regularly, you will find that any nutrients will be quickly washed away. I would make sure that there is plenty of soil or compost in the container to retain any feed and moisture and then perhaps feed with something like Vitax Q4 pellets (but not too often and especially by the end of July) which will contain lots of base elements to keep your Camella nice and green and healthy.

Thank you Jimmy. Its more disastrous than I thought but I will do as you advise.