I also had this happen with a Ball Python I got from someone. I got the hard ball out of him and he got much better. I also had this with 2 gray bands, it can mean that something else is amiss. Just watch it for a bit and put it on newspaper so you can find the fecies and check up on it. If it keeps happening, give your vet a call.
-----
Boa: 1 Hogg Island, Bulls: 3 normal, 1 Medicine Hat, Alberta, Canada, 1 Kingsville, TX Red, 1 MN, Corns: 2 Okeetee, SC, Foxes: 2 Western, Gophers: 2 Sonoran, Cochise Co. AZ, Kings: 1 Black Eastern (L.g.nigra) Todd Co. KY, 4 Coastal CA, 2 NC Eastern Chains- (M from Union Co. & F from Mecklenburg Co.), 1 Gray Banded 'Blair's', 3 Speckled, Harris Co. & Liberty Co. TX, Pines: 2 Northerns (M from NC, F from SC), 2 Louisiana (pure descendants of Terry Vandeventer stock), 1 Southern, Pythons: 3 Ball, Rats: 2 Black, Henderson Co. NC, 1 White Sided, 1 Albino Black, 1 Western Green, Mt. Hopkins, Cochise Co. AZ, 11 Tarantulas, 130 Orchid plants, 40 assorted Tropical plants and violets, 3 Freshwater Planted Aquariums with West African Dwarf Cichlids