Tesla's ($TSLA@US) institutional shareholders, who hold more than $1.5 billion in the company, have written an open letter to the board of directors criticizing the "over-committed" CEO Elon Musk and his handling of human rights, workers' rights, and regulatory issues that pose "substantial legal, operational, and reputational risks" to the electric vehicle maker. The letter also calls for the board to bring in more independent members. The letter comes after a rough week for Musk, which saw the midair explosion of the SpaceX Starship rocket, a first-quarter Tesla earnings report that saw net income decrease more than 20 percent, and a Twitter controversy, in which it removed the verified status of government accounts. Tesla shares have declined over 15 percent in the past month, eroding Musk's on-paper net worth by approximately $13 billion.