• yata-vratāḥ — those who have controlled (their senses by) vows
  Yata (controlled) + vrata (vow). The cowherds are not casual pilgrims — they fast on water, lie on the ground, and keep silence. Gauḍīya sādhana likewise insists vidhi disciplines the body so rāga can flower undisturbed.
• mahā-bhāgāḥ — the greatly fortunate ones
  Mahā-bhāga = of great fortune, having Bhagavān's bhāga (portion). The cowherds of Vraja are mahā-bhāga not because they are wealthy but because Kṛṣṇa calls one of them father. Gauḍīyas read this title as Vraja's highest title of nobility.
• nanda-sunandaka-ādayaḥ — Nanda, Sunanda, and the others
  Sunanda is Nanda's younger brother; the ādi (and so on) sweeps in the council of elder Vrajavāsīs. The verse names Nanda first because the whole chapter pivots on his crisis — Śuka is already aiming the camera.
• jalam prāśya — subsisting on water
  Prāśya (having consumed) from pra-√aś. A standard Ekādaśī-style vrata: nirjala or jala-mātra fast. Even the lord of Vraja keeps vidhi-mārga discipline — bhakti does not abolish dharma, it fulfills it.

• Whom do you keep your spiritual vows with, rather than alone?
• Where has solitary discipline been quietly failing because it was always meant to be communal?

Nanda and the elders pass the night on the Sarasvatī's bank, taking only water — keeping vrata as carefully as a sentry holds his post. Bhakti rides on a chassis of discipline; even Vraja's most beloved father observes the brāhmaṇa-set vow before the līlā unfolds.