Legal Question in Employment Law in California

In situations where employees pool their tips, tips are typically shared among employees who are in the chain of service to the customer. When a customer leaves a tip, it is usually intended for the person who serves them, as well as those who assist with the service. Based on your post, someone who performs "janitorial" tasks is not a person a customer would normally tip. Unless there is something more to this story, this would not be considered discrimination.

Of course it is discrimination. Bill Gates discriminates against his janitors by not paying them as much as he pays himself too. Not all discrimination is illegal. Discrimination in compensation between different job categories, and even different employees doing the same job is perfectly legal as long as it is not based on race, gender or other illegal basis.