If you switch between small fonts and large fonts, your labels' sizes will not be fixed.
AutoSize works only when you change the label's caption or when you switch the property AutoSize on.
The following piece of code could be run e.g. in FormCreate to fix the sizes.
for I := 0 to ComponentCount -1 do
if Components[I] is TLabel then
With TLabel(Components[I]) do
if AutoSize = True then
begin
AutoSize := False;
AutoSize := True;
end;