The only way we can successfully fill some concrete beam forms is to increase the slump of the mix. The rebars just don't allow room to operate a good vibrator effectively. These beams carry a roof over a swimming pool. Would it be satisfactory to increase the cement content to bring the watercement ratio back down and the strength back up?
It might work, but this is a classic example of bad design and dangerous practice. Design should always leave enough clearance between bars to operate a vibrator successfully. In this case the high humidity in the swimming pool area, in combination with the high-water-content permeable concrete, could lead to rusting of the rebars and structural failure. If possible, get the beams redesigned for better rebar spacing. If that is not possible use more water while at the same time increasing the cement content as you suggest. Then keep the beams permanently painted with an impermeable paint to prevent the rebars from corroding.