A certain amount of diarrhoea is normal in kittens every time their circumstances change, be that a change in diet, moving house, separating from mummy or littermates, even for some of them a trip in a crate to the vets is stressful enough to create a bit of runny bum. Kittens also don't have the most solid poo in the first place until they reach 8-10 weeks.
The key is to recognise the difference between 'normal' diarrhoea and dangerous diarrhoea when they're so small that a day of serious diarrhoea can kill a kitten so small.
I wish that everyone with an animal could learn the easy test for dehydration- pinch (gently) a little skin on the animal's back and lift it away from the animal, then let it go. In a well-hydrated animal (with the exception of sharpeis or other breeds with lots of skin folds or particularly elderly animals) the skin should shrink back to the body immediately. If it doesn't then that is a sign of dehydration and merits an immediate trip to the vets for your animal's safety.
Pleased to hear that it's nothing serious abbie.
Insecurities are about as useful as putting the pin back in the grenade.