Hi Seeker,
Thanks for the update 
Latex is the most breathable foam type but there are many factors that can be involved in sleeping temperature. You can read a little more about them in post #2 here but a waterproof mattress protector / mattress pad is certainly one factor that can make a difference because it’s much less breathable than other types of mattress protectors. If you have an actual mattress pad (vs a thinner protector) that uses synthetic fibers in the padding then this can also make a difference. Thicker layers of softer foam is another factor that can contribute to higher sleeping temperatures even with a foam as breathable as latex.
Generally sleeping temperature is the result of a combination of factors (including all the layers of the sleeping system and bedding, the person themselves, and the sleeping environment) but the first step I would take is removing the mattress pad / mattress protector to see what difference it makes.
Phoenix