Conversation so far:
What was Bless You?
In 1971, the group scored an international hit with "Bless You" (produced by the Jackson 5's producers The Corporation).
What did the hit do for their career?
The song peaked at number fifty-three on the American pop singles chart (the biggest peak of Vandellas' seventies singles), and number twenty-nine on the R&B singles chart.
What else is important about this time frame?
Reeves, out of the group temporarily due to illness, recovered and returned; Ashford was replaced by another former member of the Velvelettes, Sandra Tilley.

Question: Why was Ashford replaced?
Self-contained rewrite: Why was Ashford from Martha and the Vandellas replaced?