Why is my crested gecko egg denting?

I have it in a deli cup with a !:2 ratio of vermiculite to water. I only have one air hole but I open the container a couple of times a week. It gets around the mid 80s inside the container and the humidity is around the 50s. Could it just be that I don't have enough humidity? Or could it just be a dead egg? My female had laid another clutch before but I'm pretty sure they were dead eggs since they began to rot in like the first week and they looked different. She's over a year old and my male looks to be around the same age. I'm not sure exactly how old he is because I got him as a juvenile like 5 months ago. He looks like he's at the right size and age to breed so I don't know if it's just me doing something wrong or the eggs are infertile. Also, when I had dug up the egg it had these small red and green speckles which weren't parasites or bugs. The other clutch of eggs didn't have them so I don't know what they are. Anyways, if anyone can give me suggestions on incubating future eggs better and increasing the humidity I'd appreciate it.