Would be nice to know the details. But I think I've already provided a long-winded possible theory on the gap between g4 and g5. I can copy it here if you don't wanna peruse the forums.
[@sxcbeast](/images/3244623#comment_10744510)
Also, now that you mention it. Those new dragons might actually be from g4 as babies. I mean Spike in g5 looks slightly older than them and he was still a winged kid back in g4 when the new hatchings came.