Oh, my! I have twins and we are suffering over here too--since about the 21st! Mine are waking in the a.m. covered waist down. I have to brace myself to go into their room. The odd thing is that they have 2 to 3 loose stools then are generally ok the rest of the day.
Anyway, I have tried the regular stuff mixed in with their other foods to no avail...
rice cereal, bananas, apple sauce, toast--yogurt and milk are suppose to help too, but I am concerned that could be part of the problem for mine because of lactose issues. Mine won't drink pedialyte, or anything except soy formula and soymilk mixed. I did remove any milk-based products from their diet. Yeah, just be careful of their hydration.
Diaper rash---vaseline works as good as anything. Just change diaper and treat right away. They just need a barrier to protect their skin (not sure about any product and how it might work to treat the rash). Try not to let them sit in it, the acidity of the bm is the main irritant. Also, get rid of wipes and use wet cloth to clean. Wipes have irritated all my children (diarrhea or not). I could not believe how much that helped.
My ped says they will wait 2 weeks or more than 10/day before they do anything...
Hope they get better soon