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Overall that is part of the annual growth cycle for California sages, including Salvia leucophylla 'Point Sal'.
In the cool, wet season, lush foliage is produced, followed by the Spring flowering. As California's Mediterranean climate warms and dries in late Spring and early Summer, fewer, smaller leaves are produced and soon growth stops. In summer and fall the shrubs look dry and withered. One can often see into the interior of the shrubs due to the sparse foliage. This seasonal appearance isn't the preconceived idea for what a garden plant should be, but it is healthy and natural for these shrubs. I appreciate the dry appearance as reflective of what California's chaparral and scrub really looks like in the dry season.
You could try giving more supplemental water to native Salvia in the Summer. This might keep them greener longer, but It can also encourage rank growth and root rot that will shorten the plant's lifespan. This also nullifies the drought-tolerant benefit of these native shrubs.