What colour is their poo?
If its grey they've defo picked up a bug and its temp taken and call to vets, possibly need Tylan in their water for enzootic pneumonia, however as they're still up and about & drinking is their poo dark green becoz if they're eating a lot of grass it gives them the runny bums and fills them up so they won't eat as much nuts, I have two 10wk old weaners who are like this, happy as larry but with mucky bums, they will eat nuts eventually when I leave them in the trough.
Make sure you change their water for fresh as often as you can, you could also give them some electrolytes(calf ones from the vet or ag merchant). Make sure you clear their dunging area regularly so they're not treading in the squirts and re-ingesting it, spread some old straw there to clean it up and keep on top of your housework!
Best thing though is to take their temp anything above 39, call the vet pronto.
hth
Mandy
ps temp taken up the bum!