If you have a fan, I wouldn't worry about cold spots. the air is circulating in a small area.
I used to run 8 LG's and Hova"s at one time.
then I got three large GQF's.
chalk this hatch up to a bad experience and try again..
LG"s and Hova"s are notorious for air leakage.
I always ran a piece of duct tape around the crack where the top set on the bottom
I never candle. you lose too much heat and humidity by opening the bator.
it takes those styro bators forever to recover. my GQF's recover in about 5 minutes.. I can hatch about 1400 eggs at a time..
I usually hatch over 300 guineas per season.
to add water, use a funnel with a tube attached and poke it through a hole in the top of the bator. do not get the eggs wet.
poke the tube between the eggs and fill the reservoirs that way..
preset the bator to 100F to 100.5F without having any water in the reservoirs
bone dry.
once you add water, the temp should drop and that is the temp you will use for incubating.
if the temp rises up to 100.5F it just means you are out of water. do not adjust the thermostat,, just add water..
super dirty eggs can be washed.
don't get hung up on bluhm,, it is over rated for your small operation.
keep things clean and you won't have any trouble with infected eggs.
when/if you smell a bad egg, get it located and removed asap.. your nose is the best detector for this.
stay away from shipped eggs. pick them up in person , if possible..
don't hold eggs for more than 5 or 6 days before setting them..
you don't have to turn held eggs more than once per day.
I have been hatching eggs for more than 50 years. these things have worked for me.
I started out hatching with a kerosene heated incubator from Sears and Roebuck,
(used) .
still have it in the garage..
AND use just ONE thermometer ..
when you get one that you can trust, guard it with your life....
....jiminwisc.......