National indices were flat June 4 and tri-county stocks were nearly evenly split. The biggest loss of the day come from Westlake Village-based Arcutis Biotherapeutics, which fell 9.04 percent to close at $30.50. Goleta-based breast implant manufacturer Sientra dropped 8.83 percent to end at $3.82. Westlake Village-based real estate investment trust PennyMac Mortgage was the…