stuck shed

Hello all,

I just recieved some ball pythons that have stuck shed. Thankfully they have no retained eye caps, mainly on the top of the head that i have not been able to remove via soaking. There was some shed stuck to the back of one, which came off in a few minutes in a warm bath.
Should i just let nature take it's course and it will come off in the next shed? How long is safe to soak them? Humidity is normal, should i raise it for the time being? the last thing i want to put these poor things through is a URI.

thanks