franki
there are several reasons i can see that might have not helped the eggs.....
this is what i do with my eggs....
... leave for 24 hours to get to room temp, slightly tilted with the pointy end down. in the 24 hour period tip them once the other way, still pointy end down....this stops the embryo sticking to one place inside the egg....and only use eggs that are no older than 7 days.......the older the egg the more the fertility rate lowers.......4 day old eggs are great.
i have auto incubators so i dont have to turn them, but if you have a manual one, they need turning 3 times a day......put a coss on one side of the egg so you know when they have been turned.
place eggs in dry incubator........leave for 7 days then candle.
leave for another 7 days them candle again.
candling every day is a bit excessive, as they lose heat every time the inc is opened.
on the 18th day of them being in the inc, i turn off the auto turner, and add water......so with a manual you should stop turning the eggs.
by the 20th day you should hear pipping, and 21st day you will see the beaks breaking thru the shells.
dont be tempted to open the inc at this stage....heat loss will kill the chicks.
when chicks are hatched leave them to dry and fluff up for 24 hours.
dont worry about them starving, the yolk sack will give them all the nourishment they need for this period of time.
make sure you have the brooder ready for the chicks......and go on from there.
to be honest i never use a hydrometer in the incs, but go by the fact that an egg will lose 13% of it's weight over the inc period......if the egg gains weight the humidity is too high.
as for eggs exploding........yep they sure do.......and they smell awful.....plus they are loaded with bacteria, including salmonella, so make sure, if you do have an egg that explodes the inc is thoroughly disinfected before any more eggs are put in it, plus you can become ill with it yourself, so hygene is of great importance.
best way to insure an egg wont explode is.....only leave the eggs in the inc for no more than 3 days after the expected hatching date....and never wash eggs before they go in....if they are dirty, just rub lightly with a small piece of dry, 'wet and dry ' paper......if they are washed, you wash off the protective membrane on the outside of the egg and bacteria can get in.
hope this helps a little.