Day 21 but Candled Eggs look only 17/18 Days - Urgent Help Please.

I am after some help and advice, this is my first post so please be gentle !

I have a styrofoam incubator with 12 Pekin Bantam Eggs in - this is my second attempt at hatching as last one with 3 eggs was also a negative result.
Here are my questions I have 4 eggs which are on day 21 but they do not look like the 21 day old candled photo that I see for example some have clearer pointy ends, one has a full pointy end and the other seems too small.
After my last failure which I left the eggs in for 25/26 days I removed some of the shell off one last night to see if it was just stuck or struggling but somehow I managed to rupture a blood vessel if only slightly though, this little one still had its yoke on the outside although being at 21 days and by the morning the heat had dried it out to much - so he was buried in my garden.
I did hear tapping inside the incubator overnight last night but do not know if this was from the chick I lost this morning or one of the other ones in this group of 4, it has been quiet all day today even though I have gone into the room with the incubator in and looked/listened.

The temperature is set to 38.5 degrees centigrade with the humidity at 65 degrees centigrade.

What can I do ???

Any advice would be really really helpful.

These are my own fertilized eggs from my Pekin Bantam Rooster and my 2 Pekin Bantam Hens (1 Charcoal Frizzle and 1 Lilac Frizzle) - Would this be a weaker gene ?

And finally are Pekin Bantam Chicks smaller than normal bantam chicks - as the one from last night's head was about the size of 12mm in diameter

Many Thanks

Dr Rob & Family

Thank you for everyones thoughts so far,  I did read about the dry hatching method so over the first 15 days I was not too worried about keeping the humidity constant and only topping up the water if it fell below 30 percent humidity which It did not it stayed around 40 and obviously this was ok as they all developed normally - it seems to be only at the end I am having the problem.
It maybe just because the chicks inside are weak - and I know it is better to lose them at the latter stages than them to hatch then lose them a few weeks after - I have decided just to leave them until Saturday which will be day 23 then maybe take one and tap through the outer shell and moistening the membrane slightly to see if the chick moves inside.

Any other advice would be great.

I am also looking at getting another more automatic incubator - maybe a RCOM 20

or a Oxford one available from this company in the united kingdom - Banbury Cross Incubators dot com (It will not let me put the hyperlink as I am a new member and they are worried about spam) - this incubator can also be called a SIL one.

This may then give me a better hatching percentage.

I do prefer the Oxford one I think.

Regards
Dr Rob.

Thank you for your reply Casey,

No the Rooster is a standard white Pekin Rooster and he is one hell of a randy chicken in the morning !
I agree with the staggering this has worried me too - I may just try and do the best with these and get a RCOM 20 for the next 6 eggs which are in storage - There is one available locally and the lady will accept £100.00 (This is for a used RCOM 20)
I think this is my best option at this time.

Regards
Dr Rob.