It sounds like your email and/or case number has somehow slipped through the cracks. In situations like this where you haven’t received a reply to an email in about 24 hours (or a maximum of 48 which would be unusual for most companies) I would phone them to find out what is happening.
It sounds like your mattress “A” at least may be defective (which happens with any manufacturer on occasion) but I don’t know if your mattress “B” is normal in terms of firmness or if was also somehow made too soft. I would probably talk to them about your experience (the valley in mattress “A” and the softer feel in mattress “B” compared to the “good” part of mattress “A”) and see what they say and if you decide to replace them vs a refund then I would probably have them send two new mattresses which I would think would both be the way they were “supposed” to be (either the same as the firm part of “A” or the softer “B”.
I haven’t seen any complaints about the quality of their mattresses but you can see the details about the changes they made in posts #2 and #6 here. They are still in a similar firmness range to their old mattress so some people wouldn’t notice any difference in how they feel but the new foam will be more contouring which for some people will “translate” into a softer feel even though it may actually be more supportive.