Five classes is plenty, so I don't see why you would need to tack on another. If there is some pressing reason for taking another class now, you will have to talk to people at your school. @werunthis is right to say this is school-dependent; at my school, physics is regarded as difficult and genetics as very manageable. Additionally, "health science courses" doesn't tell me much about workload. At my school, that could mean anything from Anatomy (a ton of work) to Healthy Lifestyles (a blowoff class).
Hey sorry about not clarifying. The health science classes are online and wont require much work and effort(i hope). I also made a typo, its 2 health science classes not 3. So if I take physics or genetics it will add up to 4 plus physics/orgo lab