I have 3 male 2 and half week old rottie pups,they were thriving,eyes open,walking around but today 2 are being sick and have liquid poo,still feeding off mum but not very much.havent a clue what's gone wrong and am so worried as they getting weak.am keeping them warm and getting some cooled boiled water down them so they don't dehydrate but just want them to be OK and not sure they will,anything else I should be doing?

You should be taking them to a Vet. It oould be bacterial, it could be parvo, it could be anything. Puppies dehydrate, puppies die quickly.

Do something.

You should consult your vet!