Hmm, it's got some burnt tips on the leaves which is usually from over-fertilizing. Do you know what they've used to fertilize it? As the weather cools they need to taper back the amount of fertilizer until it would need very little through the winter, unless it's in a warm greenhouse under major supplemental lights. They need all sun, all the time.
If they can order some fertilizer that is citrus-specific that will be the best thing to use. Citrus have specific needs in the way of micronutrients.
The color of those leaves looks pretty good to me other than the burnt tips.
