Tank had a big ol poop after his mouse, and i checked it out (fun!) and i see no sign of worms lol yay!
So hopefully, just a growth spurt and some good food will fill him out =)
Runny stool is another sign of worms and or other parasites, but stress can also cause runny stool so testing by a vet or if you are able to yourselfis the best way to tell if its parasites or stress related.