A cm is about 1/3 and inch I think, then the answer in my experience would be no. But, that would be strain and limiting factor dependent!
How big they are, how far they are from the HPS, room temps also just to name a few things.
Maybe some more info and pics would help us to find an answer!
I've had 1/2 inch per day (for about a week) once. Everything was just right and the plants were about two weeks into flowering. I couldn't seem to keep up with trying to keep everything level coming out of the SCROG screen.
Ed talks about in his book that they can grow an inch a day under the right circumstances.
If they are healthy and not stretching much as compare to new bud sites coming in.... I'd be happy.
Pardon... I apologize, I didn't see that the plants were in flower. However, page 362 in "Eds book" says growth may be as much as 2", 5 cm a day in veg.
In flower, Ed states that the plant could/should grow approximately 20-25% taller and wider.
Take the over all size of the plant and divide by the number of days of flowering and it should give you a good idea of what to expect growth wise... my ad lib.
Jorge says that, properly maintained, plants can grow a half to 2 inches a day (page 28)
Both say that vertical growth is slowed during flowering but is also very limiting factor dependent. I would also suggest that it is strain dependent as well... IMNSHO!
I'm not trying to correct anyone or start a pissing contest, just quantifying my previous post.
rubadub, as JJ and PP stated... as long as your plants are healthy looking, rate of growth would be of secondary concern.
Those are looking pretty bombalicious... I wouldn't worry about growth rate, individual results may vary. Once again though... healthy bushy green babies are the main ingredient for success in my way of thinking, it looks like you well on your way!