Sorry about the late post.
The red cells dying will make them anaemic - so that means they won't have enough red blood cells delivery oxygen to the tissues. So they might feel breathless and feel their heart pump harder as the lungs and heart try to compensate. They may look pale, be a bit faint and lack fitness. White cells shouldn't be affected by the deficience of G6PD or the episodes of low red blood cells. Our red blood cells die too all the time, it's just that if they get an attack, such as triggered by an infection, they will have many old cells dying at once.
Since they are malaysian, I doubt it's very serious. So hopefully you won't notice any difference in that child. Listen to the parents, they probably no best about their child's illness and the issues surrounding it.
Hope that helps. I was hoping Han would answer, cause we haven't learned about G6PD in detail.