Hi Adriano and kmikey.
Welcome to our Mattress Forum! 
I am sorry to hear that your mattress developed body impressions and I can certainly understand your frustration at having the same issue with a second mattress after only a few days. While all new mattresses will go through a break in period and there is also an adjustment period as well for any new sleeping surface … it would be unusual that there are any significantly visible body impressions in a relatively new mattress unless it was defective.
As you are having the same issue with the replacement mattress within two weeks it may be worth pointing out a few reasons why a mattress can develop impressions to make sure that you are ruling out anything that might cause this which is not connected with the latex itself. I would first check the frame and support system under the mattress to make sure that it is perfectly flat and that there are no parts that are sagging or that are bending under the weight of the mattress and the people sleeping on it. It should provide similar support to having your mattress on the floor and you can test this by putting your mattress on the floor to see if it makes any difference. If it does then it’s possible that your support system could be part of the problem as well.
A new mattress, especially King and CalKing size, generally would not have a surface that remains “pancake flat” as the mattress loses any of its “false firmness” and the cover stretches and loosens a little. Some manufacturers use x-soft foam in their quilt panel, and/or then use 1.5"+ of wool as the FR barrier. It may well not be the latex, but the materials used on top of the latex that is causing the “indentations” and you may wish to find out what quilting and FR is used in your mattress. You also did not mention the impressions depth, but generally speaking a slight indentation would be considered “normal” if they were coming from a quilting material such as wool (which will compress in the areas you sleep the most over time) but it wouldn’t be “normal” to see visible impressions in the latex itself in just a few days.
I would be also curious about the make and model of your mattress and the materials and components inside it since there are many so-called “all latex” mattresses that are sold in the industry that don’t only contain latex and that could also include lower quality materials or weak links in their design that may be the cause of sagging. The law tag on your mattress will tell you whether there are any other materials besides latex in your mattress. While it’s certainly possible that your mattress contains layers or components that are defective … latex, in general, is the most durable of all the foam materials and is much less likely to develop soft spots (virtual impressions) or sagging (visible impressions) than other types of foam.
Impressions developed due to foam softening or breakdown is rarely an issue with latex unless it is defective or too soft for the body type of the person sleeping on it (softer foam is always less durable than firmer foam regardless of the type of foam). N3 Talalay is rated as a medium firmness by the foam manufacturer and at your BMI it should not be an issue. In some cases however a consumer can choose a mattress that is “on the edge” of being too soft for them when it’s new and in these cases even a very small amount of foam softening can put them over the edge of the range of comfort or support that is suitable for them. There is more about this in post #2 here. In these cases, the issue is not about the quality or durability of the materials but an issue of the comfort choice they made.
I hope you have the chance to let us know what the manufacturer says when you talk to them again. They may ask you to send in pictures showing the impressions (with a straight edge or string across the surface of the layers) and if you do it would be great to attach them to one of your posts as well.
Phoenix