Questions about flowering period

[Sativa]

Well a friend of mine just started flowering his 2 in a blackbox, now it's day 5 they're flowering.
The first question is do plants still grow when flowering?
And second, he has a problem on his tallest plant (located about 40 cm under the 400 watt light), he says the upper part of the plant is turning yellow... Is this normal? And what's the cause and the way to stop it from happening?

Thanks in advance

 

[sidefx]

they wont grow half as much when flowering but will grow still.
i reckon the plant is too close to the light, honestly.
has he changed the fertilizer to a flowering fertilizer.
photos.?
he might need to flush them but photos would help, and what fertilizers are he using and how often.