but they look like they're starting to dimple in the picture, which means your humidity is escaping somewhere. Before I switched to the locking tubs, which seem to seal better, I used press n' seal between the top of the tub and the lid. Just "burp" it every few days.
Same here, we found no need for press n seal with the 7qt locking lid sterilite tubs, they hold humidity better than cheap $1 sterilite 6qt tubs.