sorry cant help but hello anyway . im sure someone can help .

It is a disease called Black Spot. As the Red-Tips are related to roses, they get the same thing. Usually, the disease is not fatal... Its a foliar condition that comes about with cool and wet conditions, and often made worse with leaves or mulch around the plants. This is the one time where organic mulch isnt the best helper... Photinia likes hot weather, so placement of the plants can influence the amount of disease spread. It seems that this disease is nationwide, and common in the Fall and early Spring where air temps are cool.

There are sprays for Black Spot in most garden centres, and something like copper-sulphate (if we remember correctly) also helps. Yes, Black Spot may eventually kill the plant... but keeping the ground clean underneath the plants helps, as well as good drainage to keep the surface a bit drier. Using a rock mulch layer or weed-cloth like mulches would help some too. Trim out any badly infected branchlets to increase air-flow through the plants would help dry up surface water (like after a rain). Outside of that, keep the plants fertilized which helps also.

Hi Owdboggy. Thankyou so much for your extensive reply. I will try to put these into practise.