I found that a lot of nutrical does make their poops soft and so does the canned food. What makes it solid like a tootsie roll is feeding the dry kibble. Also, just food for thought...my baby's poop was soft when I was feeding him Eukanuba. I'm not a big fan of their food...they use by-products and Louie didn't take to it too well eventhough that's what the breeder was feeding him. I feed him Royal Canine 33 (I believe). And he chows. Maybe give that a try.
As for the mucus, I'd keep my eye on it as well. Louie had that also after a very bad day of diarhea. I didn't start him on his doggie kibble until all that mucus stuff was gone. I kept feeding him chicken with rice until his poops were firm again. Good luck.. and keep us posted.