When Dharamsee's grapes became seedless, did this happen to everyone else who got grapes?

No, the miracle of the seedless grapes was a personal experience specifically for Boss Dharamsee, seemingly in response to his inner thoughts. The narrative in Chapter 35 makes this clear. After being amazed by his own seedless grapes, Dharamsee turned to another devotee, Tarkhad, who was sitting nearby and had also received grapes from Baba. Dharamsee asked him, "How were your grapes?" Tarkhad confirmed that his grapes did indeed have seeds. This confirmation left Dharamsee "extremely surprised in his heart," reinforcing that the miracle was unique to him.