Quotation and apostrophe automatically changing to diacritical marks.

Sometime in the last month, when I use a quotation mark and then type a letter, it turns into a letter with a diacritical mark. Like -

Ä (that was typed as quotation followed by the letter A

á (that was apostrophe followed by the letter a).

I have turned off the smart code and dashes feature.

Does anyone know why this happening and more importantly, how I make it stop?

(Running El Capitan 10.11.3)