PP lower heart rate

Any other mamas dealing with a lower resting heart rate post partum? This is my 3rd baby and I don’t think I had this with the other two...I noticed Saturday it felt slower and I hadn’t had my fit bit on much this week so I put it on yesterday mid morning after checking on my no monitor where bp was 113/66 which is around normal for me but pulse was 51 and was in the 50’s resting most times when I checked yesterday. 60’s-70’s is normal for me. When I get up or move around it does go up. Of course I googled and see lots of other mamas say they had this and that it could be from prolactin with nursing, exhaustion, or just hormone changing levels. I nursed both my other two though like I said and don’t recall this. Wondering also if it has anything to do with low iron? I haven’t been taking iron but wondering if it’s low because I did feel very tired and just kind of weak/off the last 2 days. Maybe not eating/drinking enough? Ugh.lol