Please explain further... how often did you open and on what days? Which day did you lay them on their side? What bator are you using? Do you have all your plugs out?
I have not laid some on their side until even after they pipped, some people even hatch upright. Were your eggs shipped or bought local?
One trick I have learned is to move eggs to a new location daily in order to tighten hatch frame and if using a turner don't forget the motor does produce heat. I actually got my best hatches turning manually on the side and opening my bator (styrofoam, I LOVE it) at least 3-5 times per day. Since purchasing an upright auto turner and forced air (styro) bator only opening once every few days or so for candling... hatch rate actually decreased.. something to be said for attention.
An egg could be fertile and still not develop, I think. I would have broken open the non developers and taken pictures of the blastodisk/derm to see. NO, if only 8/15 if that's what was paid for with no free extras were fertile that would not be acceptable to me. But if you paid for a dozen and 8 were fertile... That about 75%... while I expect better fertility from my own flock, I think hatcheries get about that. While I would hope for more than that in purchased eggs, it kinda depends on the conversation and agreement or understanding with the seller. Did they express it would be better? What is kinda expensive? I often sell my eggs for $65/dozen and rarely less than $25. But last year I bought 3 dozen shipped eggs and had only 3 COCKERELS hatch! Oh, and I paid $250.
It doesn't sound to me like you were intentionally taken advantage of. But if you feel that way, maybe contacting the seller and gently asking for some eggs to replace the infertile ones is an option? I would only do so if you won't be irate if they decline. Maybe you can do it in a manner of reporting back to them... I ALWAYS let my patrons know that I cannot fix what I don't know and ask them to report any cause for concern. Most (local and amateur, also hatchery) peeps aren't as meticulous about their stock as I am. (over thinker who adamantly seeks the truth)
One of my favorite hatching resources...
Incubation guide
Congrats on the few that did hatch!
