That's kinda weird. The yeast don't read the same books we do, so they can be uncooperative sometimes. Usually (once they start) they'll run better than that, even if there are problems later on. Some thoughts:
Make sure you're not using the tube the hydrometer came in for a sample jar. The hydrometer needs to float freely without touching the walls, and the tube just isn't big enough. Your inital gravity reading is pretty close to what I'd guess you'd start at, but it's worth asking.
Was the water really spring (OK) or was it distilled (less OK)?
How did you rehydrate the yeast? Sprinkling right onto the mead is sometimes recommended but is stressful for them. Rehydrate in warm water instead for 5 mins, then pitch.
Was the must boiled extensively? If so it might need gentle aeration.
Champagne yeast is a traditional re-starter for its aggessiveness, though the D-47 should be fine here too.
The lack of nutrients might well be a problem; try adding 1/4 tsp (or half what's recommended on the package) of nutrients to the mead.
And rapid temperature swings can shock yeast, like your house is 70 when you're home at night but then you go to work and turn it down to 55. A one-galloner will stay pretty close to ambient temps.
Can you describe what it did? How'd the airlock bubble, was there foam on the top, etc?
Bees, brews and fun
in Lyons, CO