Sounds like you might end up becoming a victim of duck math! Plenty of support(enablers) here for that addiction...lol. I am a victim myself have 14 ducks now and am adding another breed this spring.
Was the mark or vein looking thing on the egg possibly a crack or external pip? That maybe the cause of your humidity fluctuations and if so, you do not wanna open the incubator...that is very important. If you open it during hatch it could cause them to be unable to hatch and possibly die.
Sounds to me like you are doing ok if you have movement and peeps. Just keep in lockdown and wait...duck eggs take much more patience than chicken eggs...they can be 24 hours or more from internal pip to external pip. It definitely requires patience and can cause much anxiety waiting, especially...