Generally leaf symptoms are a "trailing indicator", meaning they tell you something about what happened in the past. For instance, is they turn brown, dry up and curl up, they were probably underwatered and too hot at some point in the recent past. If the stress was less, then perhaps a portion of a leaf will show signs; maybe half will turn brown. Small black/brown spots can be a symptom of of stress, usually underwatering. In the Fall they are more likely a sign of age and coming dormancy, along with turning yellow.
By comparison, wilted leaves are "current indicator": a sign of insufficient water. This could be due to underwatering, over heating, or perhaps low humidity on a young leaf that transpires more moisture than it can take in. It is telling you about current conditions.
Generally, you have to have some sort of additional information to correctly assess what the leaf is telling you. Did you recently miss a watering day, was the weather suddenly hotter or dryer than usual, etc.
Yellow leaves in the early part of the season might indicate lack of fertilizer, or leaves that are being shaded out. In the fall they indicate the onset of dormancy. They look the same, but additional information helps determine the correct reason.