Oh, also, the line is under 16 hour grow light and in a south/west windows area at 65-68 F temperatures.

Lime...not line.

I would assess for spider mite infestation, as well as consider possible root rot issues due to over-watering or lack of drainage as the initial cause of the plant's weakening state.

Also, I would test the growing medium for pH level, as that does affect the plants ability to take up nutrients, no matter how much is there. Please do let us know if any of the above helps, and what your results were of any further testing.