I have recently received my paired-end sequence data for targeted amplicon sequencing of 18S region of eukaryotes and the quality plots seem unusual (at least to me since I have seen most of the plots used to be different). These samples were sequenced on Illumina platform using a NextSeq 300 paired end kit.
I have still running the denoising step randomly as I can't see the usual cut-off value for q score.
These plots are the result of the binned quality scores resulting from the NovaSeq and NextSeq sequencing platforms. If you have a look around the forum this has been discussed on several posts, for example here or here