How do I restore French and Dutch autocorrect on my iMac?

I often need to write emails in French or Dutch and my iMac used to detect each language and start autocorrecting in the correct one. For some reason it's suddenly stopped doing this and will only autocorrect in English. So trying to write emails in other language than English becomes a massive pain because its always autocorrecting back to English PLUS it was really useful to get grammar and spelling corrections in French or Dutch. How do I restore the different language autocorrect I used to have? BTW I use Apple's Mail not Outlook.