Start with the enclosure
Check the basics for Aphonopelma anax: fresh water, suitable moisture, a secure retreat, good ventilation and a practical temperature range of 19–26°C. A clear husbandry problem matters more than a single evening of unusual activity.
For Texas Tan Tarantulas, keep the enclosure mostly dry, with with a water dish; maintain a modest moisture gradient for juveniles. 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 Aphonopelma anax, Texas Tan Tarantulas are terrestrial 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 Aphonopelma anax, 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 Texas Tan Tarantula repeatedly climbs or paces, check enclosure shape, moisture and recent disturbance. Mature males of Aphonopelma anax may also roam much more after the ultimate moult.
One short burst of activity from Aphonopelma anax matters less than a persistent pattern combined with poor body condition or an obvious enclosure problem.
Feeding changes
With Aphonopelma anax, food refusal in Texas Tan Tarantulas is often normal around premoult, after a heavy meal or following a rehouse. Keep water available and remove ignored live prey.
If Aphonopelma anax 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 Aphonopelma anax, visible injury, haemolymph loss, severe dehydration, inability to stand normally or major loss of coordination in a Texas Tan Tarantula deserves prompt attention.
If Aphonopelma anax is physically deteriorating, correct any obvious husbandry problem immediately and seek experienced or veterinary help where appropriate.