Just catching up here.  I am not the world's biggest expert on this but I do have some experience and here is my view:
-  Get Nutridrench or those TSC sachets that Bob shared ASAP - the most important thing with diarrhea is hydration and electrolyte balance - so sachets in water and make sure they are drinking.
-  Next priority is energy - which is any food - but particularly quickly accessible carbohydrate.  A bit of honey in the water would be a good start but if they are eating then this may not be a big concern.  Honey in yoghurt is another approach.
-  Then treat the cause - likely cocci - which is the Amprolium - which technically does not 'cure' cocci but makes it less invasive and able to do its thing so helps the chicken fight it better.  Amprolium available at TSC.
-  Then finally restore their intestinal balance which is where probiotics come in - the TSC sachets again or any live yoghurt.
Hope that helps.  Hope they pull through.
