Pocket plum

Our plum tree used to give lots of lovely fruit but has had what I think is pocket plum for the last 2 years and it’s looking like it’s the same this year. Is it a lost cause or is there anything we can do? Both trees were here when we bought the house and they are planted way too close to the wall. (Maybe they grew from seedlings) They provide some privacy from the neighbours but we could plant new trees that are healthy and happier, and further from the wall. Any advice? Thanks