Last year I took cuttings from escqallonia hedging and planted up in pots, I am quite happy with how they are growing but they are covered in black spots. Can I treat these in any way or do I have to just dump them. Towards the end of last summer I asked a man in the garden shop about it showing him a sample and he suggested treating them with Rose Clear, but it didn't seem to have any effect. Any advice would be greatly appreciated.