From the photos the new growth doesn't look deficient to me. Iron deficiency shows up as pale white new leaves on most species and that is not what is happening in the photos (for reference Deficiency Finder
has pictures of iron deficiency in several species). It is usually pretty profound, not slight yellowing. Also, iron deficiency really only happens with a total lack, or very sparse iron dosing, if you are regularly adding iron a few times a week that will prevent iron deficiency. Plants don't use very much iron compared to other nutrients so you really don't need very much of it to keep them healthy. The main thing you need to keep in mind is consistent dosing. If you dose once a week, that probably isn't enough, 2-3 times a week is usually enough if you are using CSM+B. or 3-7x a week with flourish (it isn't chelated with a long lasting chelator).
Too much iron, on the other hand can cause yellowing of new growth because too much iron interferes with a plant's ability to use other nutrients in new tissue, so the tissue looks yellow.
I cannot calculate how much iron you are adding since there is no tank size listed in this post, but if you are adding more than about 1 ppm a week, that is very likely too much.
As an unrelated comment, the rotala's old leaves look a little thin but the photo is too far away to tell what is causing that. Perhaps a better photo would help if that is a problem you need help with?