Strange volcano plot

#1
Hi all,

While doing a Limma analysis to compare two groups with two replicates each I am getting this strange volcano plot. Data is comming form PCR experiment so each row represents detector and columns represent observations of the normalized Ct values.

I am attaching the volcano image and the header of my data wich seems normal:

Detector DCt.X0a DCt.X0b DCt.X1a DCt.X1b
mmu-let-7a-4373169 18.8655 3.4705 19.2245 15.6295
mmu-let-7a*-4395608 7.3955 5.1065 9.7555 6.7675
mmu-let-7b-4373168 2.2875 -0.5775 4.2425 0.3995
mmu-let-7c-1*-4395609 9.2295 7.9355 10.4795 9.0225
mmu-let-7c-4373167 2.3345 -0.5075 4.1805 0.4235
mmu-let-7d-4395394 4.4325 1.9495 6.1995 2.0045
mmu-let-7d*-4378108 18.8655 18.4965 19.2245 2.5325
mmu-let-7e-4395517 2.7135 -0.3235 4.2285 0.5975

P value distribution obtained by limma and also the DDct value seems also to be normal.

Does anyone have any suggestion of what the problem is?
thank you