Final answer:
The formation of the urine involves filtration, reabsorption, and secretion. Problems in urine formation can occur in filtration and secretion steps.
Step-by-step explanation:
The problem of Stella's urine sample showing the presence of proteins lies in the secretion step of the urine formation process. During secretion, substances such as proteins that were not filtered in the initial process are actively transported into the filtrate.
The problem of John's blood test report indicating a high toxin level occurs in the filtration step of the urine formation process. Filtration is the first step where blood is filtered in the glomerulus, and toxins are supposed to be removed and turned into urine.
The problem of Miguel's blood test showing an increase in metabolic waste also lies in the filtration step of the urine formation process. Filtration is responsible for filtering waste products, such as metabolic waste, from the blood and forming the initial filtrate.
There is no specific mention of Janice's situation in the given information, so it is not possible to match it to a step in the urine formation process.