I note that you say the soil is "even wet". Is the pot free standing or in a saucer? If the latter, it might be an idea to remove it so the soil can drain. How big is it? If feasible, it might be helpful to tip it out and have a look at the root system and checking for any grubs. There is a nasty White c- shaped maggoty thing with a dark head which is the larva of the vine weevil, which eats roots, but I've not heard of it attacking an acer of substantial size. Another reason might be that the young leaves got blasted by the recent cold snap, in which case it will probably look less than it's best this year, but will hopefully recover. I'm sure you will get other replies and advice.
