Orpington fertility/hatching issues

I have had Orps for years. We have shown them, bred them and loved them. I have kept them for over 15yrs because they are such a wonderful duel purpose bird and the show birds are still nice utility birds. About 2-3yrs ago I bought a line of Blue Orps I have played hell with ever since. Fertility is not the best. Yes, I do trim the fluff on the rear of the birds I use for breeding. Yes, their diet is wonderful and they have allot of room to graze, catch bugs etc as well as being on a good feed. They get produce year round as well.
If I load my table top incubator with the 42 eggs it will hold, I can count on about 15 or so of those being not fertile. I can count on about 5 or so coming to term, maybe even pipping a bit, and dying in the shell. Out of 42 eggs I get about 25% hatch with the rest dying either full term or some where along the line.
I have always used Hoovabator, and I have always had Orps. I have never had the issues I have had since I bought this flock. I love the birds they are very nice quality, however if I can't get hatches, they really don't do me much good.
Any advice?
Also is there some lines that are more productive then others? a large blue I could add to this line? I will add this is a 50/50 UK US flock if that matters?

 

I have 3 incubators, so Im pretty sure its not them and I keep them in my office, I write for a living so I practically live in here with the bators. Im pretty sure its the chickens. I live so far from anywhere that I would have to have eggs shipped, I can't just go buy an Orp roo. No one around here for states have blue Orps but me. I didn't know the UK lines had that issue but it very much would explain why I had my orps for years and only now since I got this flock have I had problems. Good to know.. thank you.