I think it's because this one had a lot more krausen than my first brew. I'm using the Coopers FV with krausen collar and when I pulled the collar last time it seemed to take all of that 'ming' with it!
Just leave well alone there is nothing wrong with that brew. The more you mess with it the more likely you are to introduce infections. I've seen that effect any number of times.
Your welcome, Seriously every ferment is slightly different and will give you a different effect on the top, even the same brew in a different temperature can look different.