1. The window where Brown wasn't needed in the rotation or needed to go multiple innings as a hedge before Hendricks was yanked from the rotation was a very small one. If everyone is healthy(including Brown) I would expect that Brown in leverage relief is something they would do, but they have not really had the opportunity. And he certainly wasn't failing in the rotation so if the need is there it makes sense to have him provide more value across more innings.
2. Miller threw 2 IP to finish a win in his last outing, he threw enough pitches(and it was his 3rd outing in 4 days) that he likely wasn't available Sunday or Monday. I'd expect to see him with similar usage to Wesneski, probably not being used the same days to avoid these issues with availability.
3. Wisdom is a better hitter than Canario, and Madrigal's (limited) playing time was not at the expense of any meaningful at bats that could have gone to Canario.