Oh interesting, mine is pitch black like it’s matching the color of the room I candle them in
That candler is definitely dying. Every once in a while I'll be candling eggs with my flashlight and realize that I'm not seeing as much as I should be. That's my cue that the batteries are dying and it's time to change them. One battery change later and I'm back to seeing everything clearly again.
Especially since you were able to see into the eggs well when you first candled, but now you can't - that candler isn't even shining bright enough to make out the air cell. It's dying, and you need new batteries in it or a new high powered flashight.