Phormium unwell

Could anyone advise on my phormium?

It's planted in our rockery and has been fine for at least three years that we know of. Suddenly it has gone brown in the centre with some dead leaves and others spotty. What could it be?

Thanks in advance.

 

There are 2 types of disease that Phormiums suffer, Phormium leaf spot which is fungal, and has brown or greyish spots that have a purple edge to them, or Phormium yellow leaf virus, which causes yellowing of the leaf, which then goesbon to kill the plant, and infect other phormiums, the leaf spot, which yours sounds like is treatable.

 

Thank you, Cuttings! I read about these two on a US site and it said no such diseases existed I the UK which was why I was foxed! I shall look for a cure. Have taken off dead leaves so far.