You can perhaps begin with phoning this your vet?
You are his paying patient, so there is nothing peculiar with you phoning. And yes, if the vet wants to see the kitten, or even all of them, drive in.
Begin also preparations for making home made pedialyte and such, if.
The easiest way to make a home pedialyte is take water after cooked rice (you have rice and much water, cook well over the usual time, and take away the water for using. The rice you can eat yourself even if it is a little too well done).
Add some kitchen salt,
1 litre + 1 tea spoon (3g) kitchen salt.
a classic pedialyte is
1 litre water
1,5 soup spoon (15g) dextrose (glucose sugar) - other sugars like honer also OK, but dextrose best.
1 tea spoon (3g) salt, preferably "minerale salt", but common kitchen salt oK.
Boil up with stirring, cool down. Use for kittens and kids in cases of severe diarrhea, throwing up or similiar...
Last but not least. If a kitten seems to be weak or even fading, you can try to boost some energy by giving some wetted dextrose/honey/white caro syrup on the gum.
The fading is often caused by low blood sugar contents, so this helps directly, and with dextrose - immediately.