I'm entering week 7, what's happening?

You need phosphorus. If you want to handle it organically, you can add a pinch — and I really mean just a pinch — of wood ash, for example from grilling charcoal, to your watering solution. But be careful not to use too much, as it will make the water too alkaline. As I said, just a small pinch — it helps quickly. Otherwise, I have to agree with the Organamon guy: this is definitely a phosphorus deficiency.