Different looking stool all of a sudden

[peepsmastro]

My son's beardie is 13 weeks. He's been doing great. However, the last few days his stool looks like there are some undigested worms but has the white "plug". His appetite has not changed (reptiworms and veggies), he poops at least once a day, I bathe him three times a week, his lighting had not changed, and his tail started shedding last night. I thought maybe because it is getting cooler out that upping the basking light to 150W might make a difference with his digestion, but it has not. Any ideas? Should I be concerned?