I'm sure you've already read this, but...

Two weeks really is nothing. This time of year most garters will go off food to some degree.
For example, my male radix (3-4 years old) went off food around this time last year and I didn't worry, he started eating again in Feb or March. He will often stop eating for a couple of months at a time, for instance he stopped eating between the 18 Aug and 28 Oct this year.

You don't say how old they are, and some more information about their environment would be useful if you need more advice or reassurance.