Advice please: NSW Christmas Bushes

 I'm talking Ceratopetalum gummiferum here

I have put some pics online
http://www.innerweb.com.au/ourgarden/nswchristmasbushes.htm  but to describe
the problem, we have 5 in a row.  They start out ok on the left, then
deteriorate moving toward the right.  I can't work out any difference in
soil, sun or drainage characteristics between the rhs and lhs.  We did a ph
test - pretty uniform, the soil on the happier plants showed the same
slightly acid reading as the soil on the sad plants, so we added some lime -
that was about 6 weeks ago.

We keep them well seesol'd and blood and boned, also a little osmocote 'for
natives'. The problem is displayed by the brown tips on what otherwise
appears a healthy leaf.  The larger the percentage of brown, the worse that
tree looks overall - even the happiest of the bushes have developed slight
brown tips. We have had the trees I think nearly two years.  Last year they
were perfectly happy - all uniform and well.

We are in Brisbane, but the plants are in a sheltered courtyard - they
receive some direct sunlight (each bush gets about the same amount) but it
is mostly filtered.

Any advice would be appreciated :)

 Casper wrote:

Basically, no idea. justa few 2c.

Drainage? too little?
Naturally, around Gosford in the bush, they grow on sandy soil derived
from Hawkesbury Sandstone. Dad has one at home on heavier soils, but it
is on the slope and thus drained.

Too much fertiliser?