Hi Beth819,
In most cases a protector is considered a personal item and isn’t returnable but there are exceptions that would be on each individual site. If you buy one from a big box store (Walmart, Sams club, Costco etc) they they often have a good refund policy. Some places like some of the Amazon retailers also have a return policy (especially if they are fulfilled by amazon) but make sure you check the details because in many cases it excludes shipping or has fees involved.
The Beautiful has thicker and softer comfort layers than what you have (the old Nature) and it would be more risky in terms of alignment. You may just need a “touch” more softness (which would generally be a thin topper in the range or 1-2" and this would be less risky than going with a whole new mattress with thicker comfort layers. In most cases you would have a good sense of things after a month or so but sometimes it can be a bit longer. When your symptoms “stabilize” and don’t seem to be changing much then this is a good time to consider some fine tuning if its necessary.
You can see some of the better sources for toppers in post #4 here.
Yes … all foam materials get softer over time … but latex softens more slowly than other types of foam.
The cover on the Nature is a stretch knit so this is unlikely to be the issue. It’s more likely that it could be connected to your protector or sheets than the cover. I don’t know what type of protector you have but some of the thin membrane types are less stretchy than others and they could be part of the issue as well.
A shredded latex topper that has good value and can add some softness and has less risk of alignment issues is the Seven Comforts here but they only have queen available (I can’t remember what size your mattress is).
Phoenix