Of course, Chu Nan was not sick.
The reason why he spent all 1,000 starting points in a row and exchanged them for the lowest level martial technique was precisely to obtain more points, not to mention the F-rank martial techniques that the top students of the Star Cloud Academy's Martial Arts Branch did not take seriously and even ordinary martial artists did not fancy.
To other martial artists, cultivating a brand new martial technique was definitely not an easy thing.
In particular, it was very difficult to completely master martial techniques regarding Internal Breath. It would most likely take a long time, and it was possible to use it for years or even decades.
As for cultivating it to an extremely profound level, it was even more impossible to determine how long it would take. It might not even be possible for a lifetime.