Start with the enclosure
Check the basics for Aphonopelma bicoloratum: 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 Blood Legs, keep the enclosure mostly dry, with with a water dish; avoid chronic wetness. 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 bicoloratum, Mexican Blood Legs 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 bicoloratum, 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 Blood Leg repeatedly climbs or paces, check enclosure shape, moisture and recent disturbance. Mature males of Aphonopelma bicoloratum may also roam much more after the ultimate moult.
One short burst of activity from Aphonopelma bicoloratum matters less than a persistent pattern combined with poor body condition or an obvious enclosure problem.
Feeding changes
With Aphonopelma bicoloratum, food refusal in Mexican Blood Legs is often normal around premoult, after a heavy meal or following a rehouse. Keep water available and remove ignored live prey.
If Aphonopelma bicoloratum 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 bicoloratum, visible injury, haemolymph loss, severe dehydration, inability to stand normally or major loss of coordination in a Mexican Blood Leg deserves prompt attention.
If Aphonopelma bicoloratum is physically deteriorating, correct any obvious husbandry problem immediately and seek experienced or veterinary help where appropriate.