I've a Rhododendron in the garden which has flowered every year since
planted (now a small bush size). This year it has lots of flower buds on
and has started to flower and some buds have half pushed out the flower,
then the flower has flopped. It seems to have lost the urge to continue
flowering. It's as if it has run out of energy, only half way pushing out
the flowers. The leaves still look as they have in previous years and I
can't see any insects or problems on the plant other than the flowers
failing to open. Any ideas what would cause this? The buds are still on the
plant, non have dropped off.

Thanks,
Andrew.