My solo cups are filled with a soil I mixed myself a few months back and it was probably not the best idea I've ever had. It seems likely that I over amended my mix. Looking back at the day 5 photo I can see now that there was already a problem. I'll be transplanting into 3 gallon bags with just FFOF in few days. Hopefully that resolves my current problems.
I watered after the day 14 photo so that's 7 days between waterings. That to me seems like an awfully long time but I suppose that's normal for such young plants.