Hi dgem8,
You are past the timeframe where you would be able to exchange your comfort layer so you would need to purchase an additional layer to either replace the layer that is inside your mattress or to add as an additional topper.
There is some risk involved in both directions (replacing the layer or adding a topper) because there really isn’t any way to know whether a replacement layer or topper would match the firmness or the “feel” of the vacation mattress you slept on until you actually sleep on it … especially if you don’t know the specifics of the mattress that you are trying to match.
Since you will be making a choice based on guesswork I would probably choose a topper where you can make an exchange for a different firmness level if you make a choice that isn’t what you hoped for.
If you have the medium firmness level in your Total Latex Mattress (level 6) then the top layer would be 28 ILD. If you were to choose a 3" latex topper with a lower ILD that was either one or two steps softer (which would be 24 or 19 ILD) that would give you two options. The first option is that you could use the topper inside the mattress to replace the 28 ILD comfort layer that you currently have which would be softer than your current mattress (and would give you an extra layer) or you could add the topper on top of your mattress which would be softer yet. If you purchase the topper from Brooklyn Bedding or another source that offers a firmness exchange for their toppers (a list of topper sources is in post #4 here) you would also have the option to exchange the topper you purchase for a different firmness level at a reasonable cost if your sleeping experience indicated that was necessary as well.
Phoenix