Is it permissible to reuse a tissue after tearing off the upper layer contaminated with yellowness, knowing that the inner layers become damp despite being free of yellowness?

If the moisture is from the effect of the impure yellowness (pus), then it is not permissible to re-bandage with the same cloth. The defiled layers must be removed, or a clean bandage must be used. It is not necessary to re-bandage for every prayer; rather, it is for washing away the impure discharge during istinja (ablution after relieving oneself). Maliki jurists facilitate this matter, not obliging the removal of the impure discharge nor wudu (ablution) for every prayer.