I have a pear and a couple of apple trees - did have a dwarf stock plum tree and a bruiser of a plum tree that I bought cheaply in a supermarket-style shop (possibly Lidl - cant remember).
All the plums trees performed well but the dwarf out performed the cheap huge tree every year. The cheap huge tree fruited fairly well every other year. I chopped it's height (pruned carefully I mean) - didn't seem to worry it - needs to be the right time of year (after fruiting I think I recall).
The pear and apple trees do take a bit of a break every other year as well - a fair bit of blossom but less fruit followed by a year of dripping with apples and pears.
A late frost can knock a fruit tree's ability to set fruit so that might be the cause.. I would leave yours in the ground and give them another chance. Keep well watered, remove vegetation from around the trunk and maybe give a handful of good old pelleted chicken manure to give it a boost later in the year.
Wishing you luck - nothing lovelier than plums straight from the tree
(Jam too)