Dehydratoin is not normal no matter what their size. If feel they are dehydrated, please give them some unflavored Pedialyte. Its best to give it to them using a needle-less syringe. You can purchase needle-less syringes from any drug store. Either 1cc or 2cc is a good size for them. They dont need to drink the whole 1cc or 2cc. Do this about every 30 minutes or so.
If they still feel dehydrated after 24 hours, please take them to a vet.