Problem with Pittosporum tenuifolium
 

Hi,
I have a Pittosporum tenuifolium on my SE facing Balcony in a lrge Terracotta pot,(Location IOW) it is about 5 feet high, since Dec last year the leaf tips have started to go brown, then the leaves fall, the compost is john innes no3,so I did'nt think I was over watering,could it be wind problems.
In the last month buds have started to appear.
Any help would be most welcome as I would'nt want to lose such a Nice Shrub. Thankyou.