hello vincent,
i am no expert on camellia problems but it appears to me, especially considering the white/greyish leaf margins, that it could be fertilizer burn and/or excessive salt concentrations in the soil. are you fertilizing for a reason? i.e. a soil test has indicated deficiencies in nutrient content? camellias are not heavy feeders and don't demand much in the way of fertilizers if the soil parameters are o.k. (acidic, loose, well-drained).
are you using only compost or in combination with synthetic fertilizers? some of those contains high concentrations of salts which can build up in your soil, particularly if this plant is being grown in a container.
i would also say that sunscald is another possibility, not knowing the site conditions that the plant is in.

Thanks for your response.

To dispose of the sunburn theory: it is growing under 70% shadecloth and the problem occurs in late winter. (By now, healthy new growth is appearing).

I have been trying to lower the ph of the soil (the camellia is planted out, not in a container) as the soil is naturally alkaline. Perhaps I have overdone it, as I recently obtained a (hopefully accurate) reading of 5, which perhaps is too low?

I have been using chemical fertilizers as the soil is very sandy ('gutless' according to local experts). According to the fertilizing schedule, I should add more in Feb-March. Perhaps I should omit this and not add any more compost, and see what happens. Hopefully any excesses would quickly be remedied, gaven the nature of the soil?

The mystery that remains for me, however, is why it alone is affected while two others nearly are not!

Sunburn/sunscald looks quite different.

Drying from the tip back indicates chronic -- as in long-term -- water stress. So, for any of a number of reasons, inadeqate water is getting to the leaves. Consider dry soil; root problem; stem problem; and/or excessively low humidity.

So, now it's your turn to do further homework.

Thank you.

This is interesting, as our 'soil' has quite a tendency to resist the penetration of water. I normally treat the soil at the onset of summer, but have overlooked the possible need to do so in times of ample winter rains. So, come next winter... and in the meantime, I'll just have to wonder!

Hi vincentj.I too live in perth and experience the same problem,although like you ,not on all of my camellias[I have about 100].I think it is either dry air,or lack of penetration of water,as mine all get the same regime.I don't know where you are in perth, but I go to 'pioneer' nursery in 'canning vale to purchase all of mine .they are very helpful.good luck,cheryl perth