How many days to hatch.

I have a couple pairs of Ocellaris in my brood system. Last fall there eggs were taking 8 days to hatch at 78 to 80 degrees. At that time I had these pairs in separate tanks. On November 28th I moved these pairs into a central system. I believe the temp in this system is still 78 to 80 degrees. The last two clutches have hatched on the 7th night and I am at a loss why.
Are there any thoughts on why.
I have a clutch now which is 6 days old from another pair. The eggs are dark and I still do not see the eyes in the eggs. I really do not want to lose another clutch.
So, What can I do to get this figured out?
Thanks
Mark

Eggs will hatch sooner at higher temps.

http://www.fishtalpropagations.com/#!home/mainPage
"Making captive breeding easier."

I understand that but I do not think the temps are higher in the central system than the separate systems.
I have a nest from a different pair that is 6 days old now. I will keep an eye on them and see when they hatch.
Thanks
Mark

my oc hatch on day 7 the night of and perks hatch on day 8 and tomato and clarki body types hatch on day 9 somtimes its weird my temp never goes below 80 never higher than 82 if your temp goes up and down it will depend when they hatch try and keep it constant

Thanks for the reply.... I have another hest to try this week. Hope I do better.
Mark