The heat element on one side of my (pick one) Omni, EcoFount, etc. is very hot and the other is lukewarm. What do I need to do to fix this?

The problem here is a burned out or bad heating element, or a bad connection. If it is the element that is farthest away from the thermostat, the thermostat may not be satisfied and that is why the other heater is so hot. Generally the other heating element will not be doing any heating if it is not as hot as the other side. If you have cold hands, a 50-degree element may feel lukewarm. If it is truly warmer than the surrounding components, it may have a bad electrical connection that is passing some electrical current. If this is the case, the electrical connection would probably be hot. Both heaters should always be the same temperature if the components are good. A new heating element or repairing the connection will fix this problem.