When Supergirl stops Pestilence with her laser eyes, there are two burn marks on the wall behind the CEO. As the scene continues the marks are gone.
When Kara, J'onn, and Alex are at City Hall, J'onn has the surgical mask wrapped behind his ears. When the shot changes, he is now only holding it to his face.
The doctor says that if none of the patients are contagious, they should be transferred to the "nearest trauma facility." In medical terms, trauma refers to physical injury; a "trauma facility" would not be best equipped to deal with their illness.
When Lena talks about Reign and Sam going into another dimension, Lena's accent changes from an American to an Irish one.