higher temperature

Welcome Monty. Something was clogged somewhere. If I want to change temperatures mid cook, like for chicken skin, the first thing I do is open the vents a bit. I give that about 15 minutes to see if it took. If I am not getting the temp I want, I use my ash tool and through the bottom draft door, I kind of pound up on the bottom of the charcoal grate. Does that make sense? That knocks out any ash or anything else that might be blocking the air intake. I don't adjust the vents until I see if that worked. If the temp shoots up then I adjust accordingly. If the themp is still not climbing, I bang away again until I get the desired result. This works for me every time. Sometimes I have to do it more than once, but it will open up the air ways.

Hope this helps.

Monty sounds like you are off to a good start. It could be that you were running out of lump. The egg should go up in temp no problem. Med. to higher heat cooks can use lump at a faster pace, on your next one fill the fire box all the way to the ring, unused lump can be fired again on your next cook.