I had my one and only Moderna shot in March 2021 and that was followed a couple of days later with a diagnosis of Covid, so I don't really know if the low iron levels was from Covid or the "vaccination." Between one and two months later I began to notice the difference in my hair. Not too long afterward, I visited the doctor and she prescribed the ferrous sulphate (325 mg.). It is now two -years since and while my iron is within the normal range, it is at the lower end and my hair and nails have improved but only a little. In addition, since Covid and/or Moderna shot, I've had shortness of breath—so my guess is that I have "long Covid." Tomorrow I get a stress test because of that SOB. You mention low grade temp., and I don't know how low yours is but mine never gets above 97 degrees (during Covid, however, for one day it was up to 99).