In the story about the grapes, was the miracle experienced by everyone present?

No, the miracle of the grapes was a personal experience intended specifically for Boss Dharamsee. Chapter 35 explains that while Baba was distributing the grapes to the entire group, the transformation from seeded to seedless happened only for Dharamsee. This is confirmed when Dharamsee, in his amazement, asks another devotee, Tarkhad, about the grapes he received. Tarkhad replied that his grapes did have seeds. This detail, as noted in Chapter 35, highlights that the miracle was a direct and personal response from Baba to address Dharamsee's specific doubts and internal state.