Board Thread:Legitimate Canon Questions/@comment-13895380-20160319150733/@comment-13965604-20160320160538

The answered in in a way that was sick of answering the question about a character that had been gone for a long time (about Danny)

I think visually Isaac could've pulled a few more years off as a teenager, but he chose to leave the show. Danny was looking too old though. Same as Allison back in s3, especially with her "mom" haircut. There were several times I thought she looked like she could've been JRs wife instead of daughter. Lydia is starting to look pretty old too, she's lost her baby fat cheeks.

Derek went off with Braedan and never returned because Tyler wanted off the show, or was written out because Jeff didn't know what to do with him anymore. And besides, his story arc was complete.