That was it. To fix, I went to Prefs > PackageSettings > SublimeLinter > Settings Default
and changed the first line to false.
Sets the mode in which SublimeLinter runs:
true - Linting occurs in the background as you type (the default).
false - Linting only occurs when you initiate it.
"load-save" - Linting occurs only when a file is loaded and saved.
Thanks for the quick help.