Progression of leaf discoloration what is the prob...

I think this plant is called Purple Queen. She will probably turn purple, has nothing to do with temperature rather genetics. I hope this helps.

Too much nitrogen in the past, not enough potassium now.

the first pic looks more like a K-deficiency and the second one looks like senescence/fall colors .. possibly masking the typical coloration of k-deficiency or not... depends. Every plant is different, unless it's a clone. if temperatures are falling below 68F, or even at 68F, you can cause some 'autumn' colors to come out in the plant.. may even be genetics regardless of low temperatures at night. if in hydro/soilless you can tabulate all the K you add and convert to ppm.. if it's 180-200ish, you are probably fine with K and it's just senescence. Assumes a basic well-balanced diet around 1.3-1.5EC give or take.. if running co2, you probably go higher and not have issues long-term. You can always 'go higher' short-term but it catches up within a few weeks... if provisioning outpaces use, you get a tox, simple as that... how long it takes depends on how drastic the difference is.