is she due for a transplant?

if it's dry, that could be wilt. If it's heavlily fertilized, it could be too much fertilizer. 3 weeks in solo cup? almost certainly needs a transplant. Did vertical growth stop at some point? Thats a sign the pot is too small. after transplant, give ph'd only irrigation to set the soil/substrate. Wait for a hint of deficiency before fertilizing again and dial back from before. Those look really dark and crispy unless it's just the photo deceiving me. it's possible it's a bit rootbound and that is impacting nutrient uptake too... always easier to add things later... impossible to take things out, so be reactive, not proactive.