It's not unusual for the middle leaves to bend over temporarily, so not a problem as long as they eventually straighten up and don't become soft and start to shrivel. I don't know what causes it but I do see it here, and in fact a daylily I had indoors for the winter did it and eventually straightened up. I wouldn't give any more iron until you need to based on either the package instructions or a return of the chlorosis.
Bear in mind, though, as I mentioned in the other thread, you are only fixing one nutrient deficiency (iron) whereas several other nutrients are potentially limited by the high soil pH also.
A single wavy leaf, is not, in my opinion, something to be concerned about.
