
I would take thier temperature to make sure nothing is 'brewing' if this is normal then I would feed a light meal such as white fish and potato and lay off the milk just give water at this age, for 24 hrs.
Remember you have to be care with young puppies and if you feel uneasy about anything the vet should be your first port of call
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You may be giving them too much food for thier tiny tummies which can result in the runs, remember no treats and try sticking to thier puppy meal when they are back to normal dont deviate with trying other titbits.