Hi leighecoteach.
Welcome to our Mattress Forum. 
Sorry to hear you’ve had bad luck with your recent mattress purchases and that you’re finding yourself lacking the adequate support and sleeping hot.
You mentioned you really liked the Luxury Plush mattress you had. Do you happen to know what the components of that mattress were before they swapped out to memory foam?
I am not sure if you came across some of our posts that discuss temperature regulations issues, but you can read more about the many variables that can affect the sleeping temperature of a mattress or sleeping system in post #2 here more about tracking mattress temperature regulation issues potential causes ~ Post #2 here (at least to the degree possible for a specific mattress) and the posts it links to that may be helpful. You may also be interested in the information in post #29 about temperature regulation and mattress microclimate.
You may also consider other variables such as your bedroom’s humidity level, whether your bed’s foundation allows for proper air circulation, what type mattress protector is being used (if you are using one), what type pillows/ what condition they are in, and ultimately, what materials and construction is your mattress made of. Opting for natural-fiber materials, when available in their best versions, will provide high-quality choices that are the most breathable, comfortable, and durable.
Would you be able to share the ILD of the latex layers you currently have? How long have you been sleeping on this mattress?
Thanks in advance for answering my many questions
NikkiTMU