|No, that's definetly not normal. Daytime diapers shouldn't have any odor at all basically (unless you stick your nose right where the pee is, then you might smell a slight urine odor) unless they've been sitting in a pail for a couple of days. Sometimes nighttime diapers can smell pretty strong, but even then if the odor is a burn-your-eyes kind of odor, that's not really normal either.
When you checked for suds, did you check when it was agitating in hot or cold water? It's happened to me that checking a cold rinse revealed no suds, while a subsequent hot wash (with no detergent) revealed lots of them! Also, washing soda doesn't really suds much so that could be it too. Did the stripping help at least a little?
Exactly how much of the washing soda and Simple Green are you using (not sure what you mean by a 'few'). I never use more than 2-3 (usually more like 2 tablespoons, maybe even a smidge less) tablespoons of the washing soda and 3-4 squirts of the Simple Green. If you're using significantly more than that, then build-up may be possible. This recipe is probably way less likely to cause build-up than fancier detergents with all kinds of additives, but I imagine it's still possible (especially if you have hard water).
I'd try one last stripping. Start by soaking your diapers with lots and lots of vinegar. It's been suggested that soaking in a heavy concentration of vinegar (say at least 4-5 cups, if not more, per washer full of water) could really help loosen any detergent build-up. Then strip in water as hot as possible. Temporarily up the temp on your hot water heater and maybe consider adding some stock pots of boiling water (be very very careful handling boiling water!!). Hotter water will help dissolve build-up best and it'll help ensure there's no lingering bacteria causing the odors.
I'm not sure what else to suggest if that doesn't work. You can always experiment with additives like vinegar, baking soda, borax or tea tree oil (natural anti-bacterial and anti-fungal).
Good luck, hopefully you get this figured out soon!