I have Rosa Albertine (15 yrs old) growing on a metal fence for last 2 yrs and it is not thriving. It was previously on a wooden fence which had to be replaced. The rose was not moved and is fed and given a good mulch of well rotted manure every year. Does it dislike it’s metal support which is painted with Hammerite paint?
Hammerite should not cause problems. It is more likely that damp summers have brought an increase in rose blackspot disease which ‘Albertine’ suffers from. A lot of feeding might make this worse.