Fruit Tree leaves look bad

I just took a bunch of sample leaves up to my nearby Chicago Botanical Garden plant information people and they had no solid answers as to what was causing the leaves on my fruit trees (mostly apple) to curl up. There was no sign of mites, and it's past their season anyways. Some leaves at the tips of new growth shrivel down towards the underside of the leaf. This is seen more on the young trees, in pots. I try to keep them from drying out, but maybe they are getting too much water. Other trees in the ground have a tendency to fold up. I try to maintain an even watering on these trees, but it could be a case of too much or too little watering. There is no sign of insects or fungus. We have sprayed three times this year, the last being about 3 weeks ago. The fruit looks fine, and the leaves look good except for some hail damage from a few weeks ago. There can be two separate problems here, but so far, I don't think the trees are in any great danger. The plant information guy told me to stick a pencil in the nearby soil and if it comes up dry, add water, otherwise leave it alone. Any thoughts on this?
Sherwin D.
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