Whose egg?

[Coenobita]

In the past few weeks, I have been finding a few large brown eggs along with the usual smaller speckled ones...I have a cuckoo maran from Ideal Poultry, but I'm pretty sure I don't have any other birds that would lay brown eggs. I'm guessing that the maran is laying the bigger ones, but then I'm not sure if she could be laying the smaller ones as well.. here's a picture (the top three are obviously the larger ones - the smaller one on the bottom left is the other type of brown egg I have been collecting.)

Does anyone have an idea as to who could be laying the smaller brown ones? Or could it be possible that the maran is laying both sizes? (the size difference is pretty big!)
The birds that could be laying them are: white faced black spanish, andalusian, cochin, & golden phoenix. However, I'm pretty sure that all of those hens lay white or tinted eggs...