S.K.
Sounds like they need a good stripping. There are a few different methods, you may want to google "how to strip cloth diapers in a front-load washer" or something similar. Some of your success depends on if your water is hard, what you have been using to wash thus far, etc. So the best method for your specific situation may require a little research. Also, you may want to check with the manufacturer of the diapers to see what tips or methods they recommend for their particular diapers.
*ETA: I would use bleach only as a last resort. I am currently cloth diapering my 4th child using the same diapers I bought in the beginning and have only used bleach twice. I did that when I was done using them for that child and going to be storing them for a few years. Repeated bleaching will break down the fibers and eventually ruin the diapers.