Legal Question in Employment Law in California

Unless the employer provides texting to people of one nationality and not another, or men but not women, etc., there's no actionable discrimination.

That is pretty far fetched. The employee would have to prove it was 'because of' illegal discrimination under the ADA disability, Civil Rights [age, race, sex, ethnic, religion, pregnancy, etc], Whistle-blower, or similar statutes, that the distinction was made. Other than that, the employer is entitled to set and change hours, duties, titles, compensation, benefits, leaves, vacations, holidays, policies, rules, etc. just not retroactively. Employees have the 'right' to pay and employee benefits per the state wage and hour laws and any formal company policy that may be in place, to be provided a 'safe' workplace to minimize risk of injury, and sometimes are entitled by law to certain medical/pregnancy leave rights. That's about it. There are no laws against 'unfair treatment' or poor management.