From what I understand, continuous aeration will cause the iorn to 'fall-out' and settle on the bottom of the resevoir. (it oxidizes)

There should be no reason to aerate the water for extended periods. Just a few minutes is fine.

Leaf issue sounds like possible overfertilizing. Plus, during the winter soil holds the moisture longer.

How big are the pots, what soil, what k.....

Ya know...it would really help if you filled-out the troubleshooting form as best you can. Playing twenty questions or guessing, isn't a good way to troubleshoot problems. At least not from this end, lol.