I Am Concerned For My Daughter. She Has Taken Adderall

I am concerned for my daughter. She has taken Adderall for more than 5 years for her ADD and added Zoloft for depression in the last 1-2 years. Recently, she has become forgetful, confused, sleeps a lot, unorganized in her thoughts and actions and is compromising her job because of these symptoms. I was reading that combining these 2 drugs is not advisable and could actually cause serotonin syndrome; however, can she be affected after this length of time of up to 2 years or would she have shown these symptoms right away?

Thank you