Bad fruit on my plum tree

Hi, can someone please help?
This is the second year for my plum tree to grow fruit.

Last year it had about 5 plums growing which were lovely.  However this year, I'm not sure what's happened. The seem to be going bad before they even grow?

Can someone advise what the problem is and how too fix it if possible..  

Thank you in advance (newby)

Oh no, what a gross disease!  https://www.gardeningknowhow.com/edible/fruits/plum/treating-plum-pocket-disease.htm

It looks like Plum pocket open up one of the weird ones, if it has no stone I'm pretty sure that it is plum pocket.
Remove and burn those fruit and any branches/twigs that are growing in a deformed manner, ideally do it before they turn white as that means they have already produced spores.