Ah. Yes. Well, let me forward your query to her; she hasn't a Polyamory.com account but I figure she'll be willing to respond (and then I can post it here).
From my perspective (from what I understand from her, and from what I've read on various poly forums over the years), there's NRE and there's RRE. You and A are enjoying the depths/heights of NRE, but that can spill over (as RRE) into her marriage with J. So he's not getting the short end of the stick, as long as she's conscientious and remembers and appreciates him.
I don't suppose it would hurt to ask A how she divides her attention, and to just tell her that you hope J is also getting a fair deal. Find out how she feels about those things.
All signs seem to be positive for the moment however.
Love means never having to say, "Put down that meat cleaver!"