Could be normal. Have seen it many times. Leaves are a trailing indicator: that is they tell you about the past. They show the results of conditions that existed, a couple days ago, or maybe even a week. Generally, when assessing plant health you want to know what is happening with the new growth. As long as new growth is healthy, not to worry. If new growth is healthy and normal, then you have moved on from what was happening days or weeks ago.