Start with the enclosure
Check the basics for Brachypelma hamorii: fresh water, suitable moisture, a secure retreat, good ventilation and a practical temperature range of 20–25°C. A clear husbandry problem matters more than a single evening of unusual activity.
For Mexican Red Knees, use predominantly dry terrestrial setup with a clean water dish and a small moisture gradient rather than a wet enclosure. 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 Brachypelma hamorii, Mexican Red Knees 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 Brachypelma hamorii, 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 Mexican Red Knee repeatedly climbs or paces, check enclosure shape, moisture and recent disturbance. Mature males of Brachypelma hamorii may also roam much more after the ultimate moult.
One short burst of activity from Brachypelma hamorii matters less than a persistent pattern combined with poor body condition or an obvious enclosure problem.
Feeding changes
With Brachypelma hamorii, food refusal in Mexican Red Knees is often normal around premoult, after a heavy meal or following a rehouse. Keep water available and remove ignored live prey.
If Brachypelma hamorii 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 Brachypelma hamorii, visible injury, haemolymph loss, severe dehydration, inability to stand normally or major loss of coordination in a Mexican Red Knee deserves prompt attention.
If Brachypelma hamorii is physically deteriorating, correct any obvious husbandry problem immediately and seek experienced or veterinary help where appropriate.