Plum problems

Cherry5

I have a three yr old espalier plum tree which this yr has given me lots fruit. BUT brown rot has set in and Many of remaining fruits have splits (single or y- shaped). The rot is entering through these. Having removed almost all the fruit (heartbreaking) I need to know 1) what is causing splitting (doesn't look like birds). 2) how to stop the spread to neighbouring tree. 3) How to prevent blossom rot and losing next yrs crop too? Help!