Newly Discovered Period Changes in Two mCP Stars and Updates for Previously Published Stars

We have discovered period decreases for the mCP Si stars 13 And and V913 Sco from analyzing Strömgren uvby observations obtained with the Four College Automated Photometric Telescope at the Fairborn Observatory (FCAPT). We also have incorporated previously unpublished FCAPT data in further analyses of V901 Ori, CS Vir, and EE Dra for which other investigators have reported period changes. We confirm the results for V901 Ori but find no evidence for period change in CS Vir or EE Dra. It is impossible to distinguish between discrete period change models and linear change models for these stars from the available data; this also applies to CU Vir. We discuss some possible causes of this behavior.