I would guess the leaf (being the bottom one as you state above) is just going through the natural phase and will die off completely. When it is ready to be removed, it will come off easily. If you cut it off, you will need to seal any 'wet' area where you made the cut to keep your orchid from getting an infection.
Get some batteries and post up a photo for the most accurate advice, but it sounds like you know what is going on with this orchid. If the orchid is in full bloom now (no more buds) you can unpot it and try to disturb the roots as little as possible if you fear there is root rot, but if the other leaves remain healthy, and firm, it is just normal leaf die off.
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