I have left over two sticks of 4GB ram from my new 27" iMac I just received after purchasing 32GB from crucial. I also purchased another new 27" iMac with 16GB for my mother at the same time. Can I add the two sticks of 4GB ram to the iMac with two sticks of 8GB to total 24GB? All the ram is from the latest iMac from Apple, if that makes any difference. Would there be any issues? Currently her iMac only has two slots used with 8GB ram from Apple. Two slots remain empty.