@JeanB a "rachis blight" is not too unusual after cold fronts, and is generally cosmetic. If it looks like it is quickly getting worse you could try a systemic antifungal like any "aluminum tris" (Fosetyl-Al, Aliette, etc), Banrot, Clearys 3336, or others.
I'd avoid watering by overhead spray, as this can cause or make fungal problems worse. Just water directly into the pot instead.
I'd plant it anyway, they grow 2x faster in ground...or more. Don't mess with the roots. It's best to just slice the pot off (if rootbound) and plant directly as is. Wait at least aa month to fertilize, and don't mix any fertilizer into the planting hole.