Yeah, that was my thought too, but I used distilled water with the base and it's separating. Not sure if that is a result of using distilled water instead of deionized water or something else.
My neighbor has a reverse osmosis system installed and thought maybe I would try a little of that if all else failed. lol
I purchased the base from MakeYourOwnBuzz and used the one formula they have listed. It is possible that I did something wrong of course. Here is the formula and the base is listed there as Ultra Mild.
This is either a generic version of Iselux Ultra mild or it is Iselux. Either way, I think your formula might be the problem and not the distilled water. I used the exact same surfactant to make shampoo this afternoon and it worked great with distilled water.
ETA: could be FO. I added FO and the consistency changed as well. I had to add crothix to thicken it.