Weekly update, doo-da-dee-doo:
The first leaves are still dying back on the Chemdawg x Sunshine Daydream, but they haven’t died back completely, and the wasting hasn’t spread to other leaves. In fact, this seedling is in pretty good shape, and will probably need to be repotted in the next couple of days 
In other words, I’m back to my original “the soil is probably fine” position, and therefore have no good explanation for why I can’t grow out the A13… Anyway, here’s the CDxSSDD:
My seedlings in alternative soil mixes are also doing reasonably well, though one seems to have some problematic Genetic Abnormalities™ – it’s a twisted mess of leaves growing like a vine. As my veg tent is pretty barren right now (both in quantity and quality), I’ll probably start a few more beans this weekend… just have to decide if I want to risk my finest genetics or go with cheap-o’s until I feel competent again 