Sick Toad? Can anyone help?

[UncleChester]

It may be trying to hibernate. Less light, heat, and moisture can trigger this, and two critters of the same species don't necessarily go down at the same time. You'd expect it to burrow more often if this is the case.

Is the 'bubble' on it's skin or coming from the cloaca (anus)? The latter would be a prolapse..

[GrifTheGreat]

Post some more detailed pictures of the toad and the bubble you've mentioned.