Victoria Plum help please

My tree is 5yrs old I think and year before last was fruit laden. Last year Zilch. Absolute ZERO. Since spring its been an altogether unhappy tree. I didn't know about feeding and watering etc. When it started to form lots of fruit I got optimistic. Till now. Its had a constant problem with masses of aphids and now lots of the fruit are starting to look diseased. Is it just normal markings. Is it a recognised lurgy or just because the tree is unhealthy. Ive read that now is a good time to hard prune plum trees (which struck me as odd as in fruit) but Im ok albeit reluctantly agreeable to really hacking it off and losing what fruit may survive as I luckily have another younger tree.

 

No worries @cindy...your tree will be fine though it could possibly be suffering from what I know as coddling moth...If so when cutting a fruit in half you may see what they call frask and a little maggot thingy .The way to combat it is to hang a Pheromone trap in the tree early spring to stop the moths .
The best time to prune stone fruit trees is after harvest /summer.