My 1st BM in the morning is usually (more) solid as well. My theory is that your stool sits in there all night and your intestines soak up all the excess water. By the time you have to go the 2nd (& 3rd, & 4th) time your guts don't have time to work properly, thus the watery or loose stool.
Maybe someone else will come along with another theory...
I say, keep with the metamucil regardless.