One of the first steps likely is to determine whether the jobs require overtime pay. You can look over the information provided by WA Labor & Industries to see whether overtime pay is required: http://www.lni.wa.gov/WorkplaceRights/Wages/Overtime/Exemptions/default.asp .
If no overtime paid is required and at least the minimum wage is paid for all time worked, the employer likely can work the employee without additional pay for as many hours as the employee is willing to be worked (except certain industries are regulated as to the number of hours a person may work in a certain period).
There may be strength in number. The employees can band together informally or formally (by joining or forming a union) and demand better working conditions.
Filing complaints with L&I is free. If after reviewing L&I's information, you feel that the employer is doing something wrong, you can file a complaint with L&I. Most employers in WA are regulated by L&I.
You can review your facts and options with an attorney.