Bathroom problem kitten

Question
I'm fostering newborn kittens, theyre approx. 2-3 weeks old and I've had them for a week or so now.   I started feeding them Just Born brand powder formula and ran out of it.  It was late so I bought KMR liquid formula and have been feeding it to them for the past few days.  For the past two days the one kitten has had diarrhea and the other one started to have it today.  The one weights one pound now and the other a few ounces less and they eat about 5 to 6 ounces of formula a day.  Is this what is causing it because I heard that overfeeding can cause this or is it something else?  Thank you very much for your help I truely appreciate it!

Answer
I doubt over-feeding them could cause the diarrhea, but if I were you, I would get them to the vet as soon as possible!  Diarrhea is a dangerous thing for new kittens to have.  I can cause their death!  Please get them help as soon as you can.  Good Luck, Barb