I convinced myself Nutrient Lockout was occurring during this week, so I decided to flush the plant with around 40 liters of water. In retrospect, this may have been just natural yellowing that occurs near end of life. Nonetheless, instead of just halving the recommended dose of nutrients (as is typically recommended for autoflowers), I probably should have been feeding her plain water every second day. I will try this next time and hopefully forego the flush.