Pileostegia with dreadful black spot

Hello everyone.  I've tried to google this but nothing's coming up.  This pileostegia was planted 18 months ago and has been doing ok (very slow but ok, certainly flowered and looked healthy) until the last few weeks when these black spots appeared.  My eyesight isn't the best but I think there might be a minute insect in the spots?  It's not far from a horse chestnut which suffers every year from that insect that burrows into the leaves and causes similar marks but I thought that only affected horse chestnuts.

It could be a fungus.  Just wondered if anyone had any ideas?  The climber is covered so removing the affected leaves isn't an option.  It's about 3ft high by 2ft wide at the moment and any advice would be appreciated.
Many thanks.