Your link was the right plant Glenys, I have looked in my gardening
books and there is not a great deal of information, the problem could be
lots of thing`s from too dry too wet too hot too cold :-) The leaves are
yellowing from the tip curling slightly and very brittle.

If the only thing you have done differently is add manure, my
instincts would be to look there for the answer.

Glenys
yes that was my thought too. Manure overload if there is such a thing

cheers kate