LO started Up&Up Formula & screams when she poops now! Anyone else?

Daisy166

She's on day 3 of Up&Up version of Similac Sensitive.  And she's pooped each day but poor baby screams in pain   The poops are definitely firmer than before, but not rock hard.  I also noticed a tiny tiny bit of blood in today's poop.  Like a little spot.  

Would you just switch back to SS?  I really liked that the Up&Up didn't get as foamy and DD seemed less gassy. 

WWYD?