At one week old, maybe just stick to chick starter only. Their little systems may not have been equipped to handle the seeds at all.
My full grown chickens seemed to not have an easy time with ground up FRESH pumpkin seeds, and it wasn't easy to get them ground up small enough for the chickens to want to and to be able to eat. I have added ground flax seed to mash before, but have not fed it since I started using layer pellets.. and have never fed it to little chicks.
I hope that someone with more experience in feeding chicks things other than chick starter (since that's all I ever give mine) will know the pros and cons, risks and values of the flax seeds or ground (were they fresh or dry) pumpkin seeds.
Have you ever successfully and without problems fed that to week old chicks before? I can only suggest that now you make a wet mash out of chick starter and buttermilk (or yogurt) (add a little warm water to get the right consistency if you have to)... and give it to them asap to even out their systems and set things right inside their digestive tracts. I really hope you don't lose them. Fresh water, maybe a little Apple Cider Vinegar, just a little in their water. 1/2 teaspoon per gallon? Fresh water, food and clean everything at least twice a day. Keep them warm.. I heard it like this... if you use a brooder light.... a heat lamp.. they can get as close to it as they want.. if they are "huddled together under it", they are cold... if they spread out they are warm enough.. you can raise and lower the light accordingly. It would seem that they should huddle under the lamp at night and spread out a bit in the daytime, to eat, etc... base the temp on their behavior.
I have not used a brooder.. only a brooder light / heat lamp or even just a light bulb in a desk lamp in the bathroom when they were all in the tub.
Best of luck.