Your diapers probably are not getting rinsed well enough.
For the OP- here's a crafty site I found a link to from MDC originally.http://www.diaperjungle.com/sewing-cloth-diapers.html
I love prefolds and pul covers(with gussets). The best covers I found are diaperaps, which you can get here-http://www.babysorganicnursery.com/
I also got good prefolds there. BTW- not all prefolds are alike! The more layers the better. Fortunately good prefolds are available lots of different places!
I also love my Happy Heiny's pockets, which I stuff with my. . . prefolds!!
I use an enzyme based laundry soap, same kind I use for sheets/towels/cleaning rags, etc. and I use Borax too. I like Bac-out for stubborn toddler poop. I wash my HH pockets with my prefolds, but not my covers.
here's my wash routine. . .
cold water soak cycle with detergent. If they've been in the pail for a while, I'll add some Bac-out. (I dry pail my diapers, but my covers I hang on the edge of the utility sink. pailing your pul covers w/your diaps can wear out your covers).
hot water regular wash with just a bit of detergent and some borax. I don't usually need an extra rinse. However, as one of my instructions sheets states- "occasional sun-ing of clean wet diapers will minimise stains" so I hang them out when I can, then toss in the dryer to fluff.
WARNING to newbies!!! Cloth diapering can be addictive! there are so many neat things to try!