Heaven, that does sound colostrum. When you are still feeding an older child, your milk will change to colostrum at some time in the second half (usually, sometimes earlier) of the pregnancy. This is still great for your DD so there is no problem, but many mums do find that the poos go back to being more new born like when they are getting the colostrum again.

I am not sure why it is clearer during pg than after the birth. I guess it's just like breastmilk in that the composition is always changing and it becomes more concentrated after the birth.