Hi Frustrated Mattress Shopper,
I don’t know any of the details about your weight or sleeping position or the specifics of your mattress but it doesn’t sound so much like the mattress is degrading with only a 1’ quilting layer on a solid core of latex and it sounds more like your mattress may have been too firm in the first place and may not have a thick enough comfort layer to provide the pressure relief you want.
I would also read post #2 here which may have some helpful suggestions including making sure you talk with the manufacturer of your mattress about any suggestions they may have.
Since your mattress is likely to have an even surface (with only an inch of polyfoam there is little to break down in the mattress) it seems to me that a topper would be a good solution and post #8 here has some topper guidelines that may be helpful.
I would tend to be very cautious with the PLB toppers because they are very soft and would normally be more suitable for very light weights and you may do better with a firmer topper than 14 - 15 ILD … again depending on your weight and sleeping positions.
Phoenix