As part of my Thanksgiving preparation, I made a chicken and turkey stock by first roasting the bones and then cooking them very low for a few hours. About an hour or so before the end of their cooking, I added roasted vegetables -- a combination of onion, carrot, celery, parsnip, turnip, and parsley root. I didn't add any other flavoring other than a touch of salt. (I know most people don't salt their stocks, but I tend to undersalt everything, so adding it at every step will help.)
My stock is tasty, but rather sweet. Is this a factor of too many sweet vegetables (or not enough celery)? Or is there something else I'm missing?
(I compensated in my gravy by adding a touch of soy sauce and fish sauce to add more umami flavoring. But I'd like to understand why it happened.)