"Look tired" is not very descriptive.
1) Post your latest water stats, if something like the nitrates are high, this stressor may be making them seem 'tired.' The very first thing anytime you ever even think there may be a problem is to do as many tests as you can. It is best to eliminate as many problems at the beginning, and knowing the water stats is the beginning to many issues.
2) Describe the tank better. Do the cories have plenty of places to hide? E.g. rock caves, and under plants, and under branches, etc.? Cories need to know that shelter is nearby. Like with a great many fish, they will come out more and be more active if they know that safety is just a few swishes of the tail away. If they do not have sufficient cover, they will feel stressed and may be trying to be as still as possible ('tired'?) so that they think no predator will see them.
2.1) In a similar vein, sometimes cories become much more active nocturnally. Loaches, too. They usually are more comfortable coming out with the lights out, because predators are far less active at night. Are the fish still 'tired' with the lights out?
3) How many cories are in the tank? They are a social fish, and need groups of I'd say at least 6 or so to be really comfortable. The more, the better. And, the more comfortable they are, the more active they will be (and the less 'tired').
Finally, I want to urge you to again better describe what 'tired' means. The better the description, the better the forum members can help you.