They have probably found a spot they like and are comfortable there. My black phantoms (your Glotetras are GM black phantoms) arent active swimmers throughout the whole tank. They tend to just stay in their territory.
As for feeding, i would give it a few days. If they are nervous, then they will not be inclined to eat. And i have to be straight here. From what ive read about glofish, if you get 2 out of 3 survival you have done well. Glofish are illegal here, so ive never kept them (or even seen a real live one) so i cant comment from first hand experience.
The water colouration is tannins. Thats really beneficial for the fish. It can take months of soaking to remove tannins, a few days wont do it. You could boil the wood to remove a lot more a lot quickly, or if you wanted to to deal with it in the tank, activated carbon in the filter will remove it from the water. Is the colouration just affecting the area around the driftwood? That might indicate a lack of good water flow.
A note on drip acclimatising. The reason to drip acclimatise is to gradually adjust the water from the parameters it arrived in to the parameters of your tank. Its a sudden change in parameters that shocks the fish, which shouldn't happen with drip acclimating. If the water from your fish store and your tap water are similar there is no need to drip acclimate. I very rarely do this. Drip acclimating "can" be a bad idea with mail order fish however.