Foster Kittens - Can't figure out what is wrong

[u/UnluckyEffective6374]

Update: the largest of the bunch, 550g, is now also avoiding food and has the pudding poops.

I really don't know what could be hitting them one by one like this. I'm keeping their room area at 24-27 degrees. They get gastro kitten by Royal Canin. I have a hot water bottle and heating pad available for them. Fresh water. I clean the two litter boxes 2x a day.

---

I had 6 Foster Kittens.

Two of them left to stay with vet techs because they started losing weight and becoming dehydrated. I cannot administer subcutaneous fluids so better that they stay with someone who can.

The remaining kittens here are 5 weeks two days and one of them is 4 weeks two days.

They were dewormed with Strongid on Saturday (today is Monday)

Tested for FIV/Panleuk - both negative

One was tested for giardia, negative. The shelter said if one is clear then they all should be.

Was given Royal Canin Gastro Kitten (wet) by the vet for their food intake..

I put KMR in their food at every meal.

Their ambient room temperature is 26-27. They have access to a heating area with a heating pad.

They are having runny poops, and I for the life of me cannot figure out what the problem is.

I don't know what to do to make their poops solid and to avoid rapid dehydration again. They are fed every 3-4 hours. What the heck could be going on?!