Absolutely delighted to hear your hen is picking up. Well done you!
I don't know if there is something else added to the DE that is marketed under the brand name "Smite" here in the UK (it states that it is an organic treatment) but it has certainly worked for both myself and my neighbour, who had a really bad red mite infestation earlier in the summer. He literally found piles of dead mites under the roost bars each morning for a few days after using it. I'm onto my second 1kg box of the stuff and would not be without it as I find it very effective too. I don't know if it is food grade or not and I've not used it for worms as it is not marketed for that but works really well for mites and lice for mine and my neighbours hens and hen houses.
We can all only speak from experience and I certainly wouldn't persevere with it if I hadn't seen good results, as it is about £9 for a kilo (2.2lbs).
I wish I lived near you as I would have happily taken your unwanted DE off your hands.
Regards
Barbara