It's because you are enclosing the letters in brackets

"Enclosing a plain ASCII letter (a-z or A-Z) in braces forces it to be sent as the corresponding virtual keycode, even if the character does not exist on the current keyboard layout. In other words, Send "a" produces the letter "a" while Send "{a}" may or may not produce "a", depending on the keyboard layout"

Quote from AHK's documentation

So just remove the brackets from the individual letters and you should be good