F4 being the 4th generation.. or would it be fifth? I don't recall right now how that works.. too tired.
How old is the first generation.. or how hold were they when they died? If they are all still living, you can't really say whether or not they will make it through their lives health problem free. Things may crop up eventually. What type of breeding have you been doing, line breeding or another method? Have you been keeping track of all of the babies and monitoring their health from birth to death? Have you ever figured out what they carry?
One other question... even with 4 or more generations, unless you've bred over an extended period of time, how are you able to already be mentoring people? Seems a bit soon personally, if you haven't been breeding for a number of years. Remember, mentoring is something that someone can do with you indirectly, through email or phone conversation. You could find more experienced people that way.