I've noticed a problem with some of my tomato plants this year. They are growing at a similar rate to the unaffected plants and they are still lproducing fruit and suckering as I would expect. It is just that the leaves are underdeveloped and not opening. It is affecting several varieties of tomato plant as well (mortgage lifter, amish paste and blueberry, although blueberry has the most plants affected). I have grown all these varieties before without this issue. Attached are some photos.