Cutting back the Nassella (Mexican feather grass) is probably a good thing :-) It self-seeds extremely readily, particularly in mild climates and is borderline invasive. I wouldn't be at all surprised to see this appear on California's invasive species listing in the next few years. I no longer sell it at my nursery because of this unpleasant trait. I'd recommend cutting back the seedheads (at least) as soon as they extend above the blades.

I'm not sure how the blood grass will respond to a severe cutting at this time of year. The dry, brown blades indicate it was suffering from lack of moisture - this is a grass that prefers a moist soil location. It too can be an aggressive spreader in the right location and subject to reversion to the highly invasive species form. Sale of this grass is also restricted in certain areas.