I agree, it must be so difficult growing a plant to the end in a solo cup, I imagine the plant's using up the available N, P or K that they need at this stage so quickly, leaving a residual nute mix containing the elements they don't need. She then stops feeding until you replenish the nutes, and the cycle goes on and on. Any way of getting her in a larger pot, while flowering's early? Or feed her much more often, 2, 3 or 4 times a day?