The celebrated group of poets in medieval Mathura and Vrindavana called the Ashta-Chhap were the successors of which one of the following medieval Bhakti Saints?

The Ashta-Chhap (Eight Seals) was a group of eight medieval poet-saints who lived in the Braj region and were dedicated to the worship of Shri Nathji (Krishna). These poets were disciples of the Bhakti saint Vallabhacharya and his son, Vitthalnath. Surdas, the most prominent among them, was a direct disciple of Vallabhacharya and is celebrated for his compositions in Braj Bhasha that romanticize Krishna's divine pastimes. The group was formally established by Vitthalnath, who selected four disciples of his father (including Surdas) and four of his own to form this prestigious circle of kirtankars. While Kabir, Chaitanya, and Guru Nanak were contemporary figures of the Bhakti movement, they belonged to different traditions: Kabir to the Nirguna Sant tradition, Chaitanya to the Gaudiya Vaishnavism of Bengal, and Guru Nanak to the Sikh tradition.