Marmots are pretty good quality. If you're wearing socks and your feet get cold, take them off. If you're not wearing socks and your feet get cold, put some on. If you're wearing more than one pair, they might be restricting the circulation so take some off.
But most of all make sure your head is warm. If you're not wearing a hat or the bag's hood, your body redistributes blood from your extremities to keep your head warm....so your head still feels warm and your feet start getting cold. Put on a hat and your feet warm up.
Sometimes people get cold feet in hammocks, too. If your feet are higher than your head, it can cause it. And the lock-knee that folks are talking about in the other thread. Also, depending on how I'm hanging, sometimes my toes stick up over the hammock body...and catch more wind than the rest of my body.