another simple question about hooks

[David Rod]

(defun david-r-turn-on-text-stuff ()
  (flyspell-mode 1)
  (abbrev-mode 1)
 )

(add-hook 'text-mode-hook 'david-r-turn-on-text-stuff)

this works fine.  I want to add a (mark-whole-buffer)
(canonically-space-region)
Whenever I try this, this renders new messages and follow-ups
 by gnus inoperable 
Also another question.  is there a hook by killing a buffer which
contains a file with the extension as .txt ?

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