Thanks for all the ideas!
I still haven't figured this out... but here's the latest: I went back to the cloth diapers yesterday after a few days of just 'sposies and sure enough, the rash is back! So all of my stripping and deep cleaning was for naught. Only good news is that the stink is gone.
I'm afraid that the synthetics are the problem, along with the fact that I can't get the washer to do SUPER hot washes. (We just moved into a new house and figuring out how to turn up the hot water heater feels like too much of a production for me right now.)
Last night I made my own detergent from Borax, washing soda and Fels-Naptha. I used that on this morning's load of diapers but since they've been drying in the sunshine all day no verdict on whether or not the new deterg causes a reaction/gets the yucky stuff out yet. I skipped the lavender EO and bio-kleen today too, as someone suggested.
Next step will be boiling our prefolds and using those exclusively. Can anyone walk me through the boiling process?
(Another thought: Could the rash be a food sensitivity? DS has been crazy for kiwis lately - he ate a whole one yesterday, but none the few days before... so maybe that's contributing? Argh! )
Ok, and last but not least, if we do wind up switching to flat/prefolds, how do I get DH to convert from the pocket dipes? He says, "I can change diapers and I can do origami, but not both at the same time." We need a super-easy method that he can master with minimal stress.
Thanks again for all the help! You guys rock.