I've been cooking a 7 pound butt for the last 15 hours and noticed the Butt temp dropped from 171 to 163 when I got back from lunch. The BGE temp was around 240 at the time but was hovering around 200 when I got back. I quickly opened the vents to up the temp to around 240. Do I need to open the grate to check and see if more lump is needed? Will this butt ever finish?