The indent signals a change, like a paragraph change would. The first stanza of the poem is background information about the mother and daughter. "The sky has been dark / for many years" is metaphorical, as it cannot be literal; it relates to the state of the daughter's mind, emotions, and life. Her mind is overcast, as with clouds, as she is trapped in her duties to her aging mother. Her skin "has become as damp / and pale as rice paper" because she has spent all her time indoors for years, working and worrying over her mother. It is also a metaphorical reiteration of the lack of sunshine in her life (literally and figuratively). She then reflects upon how her mother's skin had become parched when she could still work in the fields.
The second stanza is a shift to the present: "Lately," and "This morning," where she goes through the daily tasks of caring for her diabetic mother and sees no escape from this cultural prison until her mother eventually passes away.