Got all my test results back from my first oh visit. Everything is good except for really low iron.…

Got all my test results back from my first oh visit. Everything is good except for really low iron. Its weird because my iron was great my whole first pregnancy and even 3 days after I had her it was still a little above what mine should be, Ive been making sure to eat lots of iron filled foods and taking prenatals. Im stumped as to why its low lol