Pork Butt Temp Dropped

Hey all quick question, I smoked two 8lb butts overnight, on my LBGE went well temp locked in at 250 dome grate read 230ish constant. Turned and basted both after 8 hours, and they were reading in the low 170's. Temp hit 183 on one, and 190 on the other, so i opened up and used a thermapen to double check. wasnt getting consistant 190's, more like mid 180's, so left them on. Temp has since dropped to low 170's on both. lid wasnt up long either. Im not sure why, thought i was past the stall they went on at 12:30am last night its now 5:00pm, so should be done. I  have thermoworks calibrated thermocouple meter and a thermapen, plus a backup so i know there accurate. Is this strange? let them go? Theyre still on, and i hope ok! Thanks in advance!