Hey there - This is what I would do:
Make sure they don't have signs of illness:
http://redearslider.com/index_health.htmlRealize that while for a positive reason,they are in fact going through several adjustments: a new home (stress #1); a new way of being fed (#2); and a new face caring for them (stress #3)
Who knows what their life was like before you got them - who knows what they are used to eating, or how humans treated them.
They were home four days and didn't eat (probably because of stress of the new environment). So, if I am calculating correctly, they have been exposed to a new feeding routine for three days. While a great choice, it is still new to them. Give them a little time to adjust to their new home and to realize that you are not a threat (caution is an instinct for animals and people alike)
I will reiterate and emphasize ***if,
and only if, they are not showing
any indications of illness**then they can go several weeks without eating.
Illness, less-than-optimal water temperature, inadequate or incorrect lighting, and a plethora of other things can affect their appetite.
These little guys can be quite stubborn when it comes to "breaking" them from food they love (i.e., whatever they ate before you brought them to their new and permanent home) - Combine that with the stressors mentioned above and it's not surprising they haven't eaten yet.
It's only been a week. It's OK. If you are
100% confident that they are healthy, and their habitat is optimal, then find peace in the fact that you are not starving them. You are giving them food and they are choosing not to eat.
The best way to alleviate any concern is to take them to a vet for a "welcome to my care" checkup
Then you can walk away with the confidence that they are healthy.
Sorry, I should have warned you that I am the Queen of Vet Soap-Boxing

Absent a vet, give them another week.
If they still don't eat, well...time for a vet
