Sounds soooo familiar, Rob. Sorry, I don't have Orange Heads, but I do have Abiseo and they are an absolute pill to breed. I had the same situation where I had 2 females and one got thin and died. I think they can be really aggressive toward each other. My 1.1 (remaining) have a love-hate relationship. They try to breed periodically, but they will also wrestle quite a bit which is disconcerting, partly because of the size difference between the male and female (I am not 100% sure this is always the case). They are in a 90 gallon with just the pair and it is scaped with a ton of visual barriers. Not much more I can do on that front.
I am in the same boat as you are where I am the only one I know with a female so I feel a real burden to get some offspring out there to preserve them in the hobby. Further info I can pass on is that before they breed, I will hear quite a bit of calling and the male will wait for the female in the coco hut. Once I see both in the hut, I will usually look to find him on top of a clutch of eggs which may or may not be fertile. This happens every 6 or 8 weeks during the summer and occasionally during the winter.
Do you have moving water in the tank? I go out of my way to tell folks not to put water features in their dart frog tanks, but Ameerega seem to be an exception.
Once you get eggs, your battle is far from over, if my experience is any gauge. Mine will lay completely infertile clutches maybe half the time. Even if a clutch is fertile, mine will sometimes eat them before they hatch (I had been allowing the male to sit on them until they hatch because I was told that's what has to happen). When that happened like 3 clutches in a row, I started to pull them. They did just ok the last time, but I did get a few tads out of the deal all but one of which perished when I moved them to the tank I had prepared. I learned a lot from Tijl's thread about breeding his Hahnelli (sp?). It doesn't seem to be 100% the same between that species and pepperi, but it is closer than pepperi to any other species I have bred. Thanks, Tijl!
Anyway, I wish you the best of luck and I hope you have great success soon!
Mark