UPDATE
So I moved two of the larvae to the new substrate(couldn't find the third). I will pick up the container to check on them but no digging, except on Christmas. I barely dug through one container with no signs of anything, but later in the evening I found my smallest grub burrowed up against the container wall...and it wasn't so small anymore. Easily over 1 inch. Seems like it's working...I hope.
So I moved two of the larvae to the new substrate(couldn't find the third). I will pick up the container to check on them but no digging, except on Christmas. I barely dug through one container with no signs of anything, but later in the evening I found my smallest grub burrowed up against the container wall...and it wasn't so small anymore. Easily over 1 inch. Seems like it's working...I hope.