The end bottom tubes with crystals and one-two inches on the left and right sides seem cooler. Is my mat defective?

All Ereada® amethyst heating mats and pads use the same very safe double silicon and Teflon insulated titanium heating wires under several layers. The heating wires are positioned at a little distance from the mat’s edges for extra electrical safety.

So, the end tubes with crystals are heated indirectly by other stones. The longer the mat heats up warmer the end tubes and mat’s edges will be. That is why initially, you might feel like not all stones are equally hot. It is totally normal and has absolutely no effect on functionality.