I don't own a hygrometer but you can bet I have multiple thermometers in my inc, I trust my herpstat but it only reads temps in one place.

If you are using 6qt pop top sterilte tubs those are more than ventilated, they flat our lose all humidity without using seal a meal, at least that was my experience with thos cheapo tubs.

We use 7qt locking lid sterilites, like this one...


I don't use vermiculite anymore and that incubator has been "remodeled" lol, but those are the best tubs imo, but like most things sterilite they quit making that tub and are now putting out 6qt locking lid modular tubs.