I think it's something to do with the weather. I've been told that they need plenty of water in Summer and Autumn in order to make flowers for the following Spring.
I too had one that went yellow and finally died, but my surviving one is doing well so far this year.

Camelia,s like an acid soil that they can get their roots into, not just a bit of ericaceous compost, they also need a position in which they don,t get early morning sun,so that the flower petals don,t get scorched, also having moved them twice in three years will not have helped, because they don,t like root disturbance.
If you don,t have acid soil, I would give it a feed of something like sequestrine a couple of times a year.
regards Derekm.

Agree with Derekm - go and buy some Sequestrene tonic and apply according to the instructions on the pack. You can also buy a special feed for acid loving plants, but frankly, if you're using sequestrene as they tell you to, you won't need the acid feed, just something like Growmore will do just as well.

The yellowing of the leaves is a kind of anaemia because the plant can't take up iron if the sol isn't acid enough. Sequestrene puts that right. You can also use plain iron sulphate which is cheaper and for me works just as well though some won't agree!

You'll be amazed at how quickly and brilliantly sequestrene remedies acid-soil loving plants' problems. I received the same advice from Goy members for my big, yellowing and distinctly unhappy hydrangeas last year, gave a single dose of this, and within not much more than a fortnight, greenness and vigour was very evident. They are already in full leaf this year, and still look healthy and happy.