Is ablution annulled by normal vaginal discharge? Is it ok to apply henna during menses?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Vaginal discharges nullify the Wudu.  So, after these discharges you need to refresh your Wudu.  As for applying Henna, it is lawful during menses.  It is also lawful during period of purity provided it does not leave a layer that prevents water from reaching the skin.  So, henna product should be removed before Wudu or Ghusl as it prevents water from being in direct contact with the skin, which is a condition for the validity of both Wudu and Ghusl.

Allah knows best.