Unless this dry weather has completely dried the roots at some point, I don't think you need to worry and that's very unlikely. I bought a persimmon from Germany that didn't break dormancy till August! Some trees are kept in a chilled environment to prolong the dormancy and this was the case with the persimmon. Check over them to look for healthy looking dormant buds and scrape a bit of bark, looking for green underneath. Despite the weather it's still early and some established plants remain dormant, they are also the 'sensible' ones because late frosts are still a possibility. Far from a lost cause, I think you'll see them start in the next couple of weeks but don't worry too much if some don't.

If you planted container-grown trees, the roots have to leave the shape of the pot and start foraging as well as multiplying.

If you planted bare-rooted trees they have to get over the shock of being transplanted. And they probably haven't got a lot of feeder roots to get going with. They'll be calling on whatever's been stashed in autumn in the branches and trunk to get themselves into growth.

What you need, for success, is root growth ahead of top growth. When you planted out, you hopefully trimmed back the branches (unless you bought the trees pre-pruned) so that those roots can get on with both establishing anchorage AND feeding the waiting buds. And you've added a stake and ties so they don't get rocked out the ground by the wind.

Even if the weather is dry - don't over-water at this point. There are no leaves to wick away the water and the roots could be sitting in a swamp, desperate for air. A bucket each (10L), once a week should be plenty in dry weather, for now.