Start with the enclosure
Check the basics for Ephebopus cyanognathus: fresh water, suitable moisture, a secure retreat, good ventilation and a practical temperature range of 22–26°C. A clear husbandry problem matters more than a single evening of unusual activity.
For Blue Fang Skeletons, use moisture-retentive lower substrate with good airflow and a water dish. If the enclosure is obviously too wet, too dry or difficult for the spider to use normally, correct that issue before looking for a more complicated explanation.
Know what is normal
For Ephebopus cyanognathus, Blue Fang Skeletons are fossorial tarantulas, so normal retreat use should make sense for that lifestyle. A hidden spider is not automatically a stressed spider, and a visible one is not automatically comfortable.
With Ephebopus cyanognathus, changes from the individual's usual routine are more informative than a generic list of 'stress signs'. Compare activity, feeding and retreat use with what the same spider normally does.
Climbing, pacing and restlessness
If a Blue Fang Skeleton repeatedly climbs or paces, check enclosure shape, moisture and recent disturbance. Mature males of Ephebopus cyanognathus may also roam much more after the ultimate moult.
One short burst of activity from Ephebopus cyanognathus matters less than a persistent pattern combined with poor body condition or an obvious enclosure problem.
Feeding changes
With Ephebopus cyanognathus, food refusal in Blue Fang Skeletons is often normal around premoult, after a heavy meal or following a rehouse. Keep water available and remove ignored live prey.
If Ephebopus cyanognathus stops eating but remains well hydrated and otherwise behaves normally, observation is usually more useful than repeatedly opening the enclosure and offering food.
Changes that need quicker attention
In Ephebopus cyanognathus, visible injury, haemolymph loss, severe dehydration, inability to stand normally or major loss of coordination in a Blue Fang Skeleton deserves prompt attention.
If Ephebopus cyanognathus is physically deteriorating, correct any obvious husbandry problem immediately and seek experienced or veterinary help where appropriate.