If you use mhwd-kernel you should get the headers too - that is if they are present.
Since you earlier mentioned dkms - I assumed you had kernel headers - as they are paramount for dkms to be able to generate the modules.
I also saw that you installed linux-headers - but then you have to select the correct package(s) - otherwise you get the first one listed linux419
Remove linux419 and install headers for the remaining kernels
sudo mhwd-kernel -r linux419
Then install headers by specifying
sudo pacman -Syu linux610-headers linux611-headers