It's always important to be in the habit of reading immediately after writing. You may also want to try multiple prompts. Let students write for three minutes on one prompt, then introduce a second prompt. My students try to incorporate the new idea into the flow of their existing writing. After three more minutes, introduce a third.
Writing is only one form of language use.
There are many ways to open students up to the possibilities that language provides for expression other than putting pen to paper. Invite students to bring instruments and use them to improvise songs, or as background for improvised dances or scenes. Turn on a tape recorder and capture students as they improvise stories or poetry or dramas orally. Get together with the drama, art music and dance teachers. All forms of creative expression feed each other.