Hey Jennifer,
This is an Australian native so they do not like phosphorous in the fertiliser as it damages their roots. It sounds very much like you could have used the wrong type. (BushTucker by NeutroG is best). This could well be the reason for the leaf loss. The only thing you can try is a fertiliser with plenty of nitrogen in it (but no phosphorous). This will promote new leaf growth, but if the roots are past repair then it may just be too late. If in doubt always use Blood and Bone on natives.
Jennifer - Edensor Park: WE have a gorgeous green wall with this plant.. but might have accidentally fertilised with wrong thing as its leaves are now yellowing and dropping on the lower branches. If this is the case... any antitode suggested? Such a shame it is a magnificent wall covering the Colourbond. If this wasnt the case (am checking into this) what else could be wrong? It gets plenty of sun and we water well once a week or so ... we didnt trim enough at the base as it grew as we were mesmerized... so its very top heavy. SHould we bite the bullet and trim it hard to regrow?.