@Rich92 Yes, this grace period appears to have expired. I don't think the circumstances you describe would qualify for a penalty-free cancellation. You could try pleading with your guests to cancel from their end - this should be possible as long as they placed the bookings before 14 March.
It might also be necessary to develop a more sustainable agreement with the others in your building, especially the more vulnerable, before considering bookings for July and beyond. Is their request more "let's wait and see," or do they feel confident that conditions will be safer for them in July?