Probably because of the changing weather we have had our summer by the looks of it in Yorkshire lol. I lost mine after pruning it hard so I have forgotten when it changes to red or when the little cream flowers come but I wouldnt worry about it as long as it has leaves.

I think you have a misunderstanding about the red leaves on a Pieris - the new leaves on a Pieris always come through red (depending on the variety) and then turn to green as they age - the reason you see so many red leaves in spring is because the plant is bursting into growth after being dormant all winter - new red growth now is fine, and that's what you're seeing, not reddening of the leaves as autumn approaches - deciduous shrubs show colour changes in autumn, Pieris is evergreen, so doesn't.

thank you both with your help, its much appreciated