Ragdoll kittens runny poo

I have recently got 2 Ragdoll kittens Charlie and Leo 13 weeks old (5 days ago) both otherwise well, full vaccinated and had worming treatment 3 months ago. Lively and energetic.  They have had terrible runny poops on and off since arrival. I have been giving them the same food they were having before except they did manage to eat some of the older brothers food the last couple of days (I have two older ragdoll cats as well age 2 Jack and Tom). I realize this is probably the reason for the tummy upset and I am being strict and will keep them just one type of food they had before. Charlie has one episode of runny poop with blood yesterday but none today. I contacted an online vet who advised Prokolin and Panacur. I have been trying to get the prokolin into them but it is difficult and I am not sure how much they actually had. (I am on my own so difficult to hold them and administer it.) I just wondered if there is anything else I need to do to help with the loose poops. They have been drinking as well as I know dehydration is a risk. Thank you

Hello!  Three months sounds like a very long time ago for the last worming treatment at this age, so you definitely need to pop them to the vets for a weigh and a worm.   I hear what you say about the pro-kolin - sometimes squirting some onto the paws can be useful as cats are very clean and may try to luck it off!  However do stick to the reccommend ed dose in a day.  If diarrhoea continues for more than 24 hours (or however long your vet who has seen the patients has indicated, or if they seem at all less bright in themselves) then a vet appointment to reassess hydration may be a good idea.  As you say, kittens can become quite dehydrated quite quickly. Best of luck with your two little bundles!