I have some rna-seq data and they all have this odd extra peak in GC content. Adapter trimming was carried out using Skewer to produce trimmed reads. The adapter contamination is now gone but the GC profile still looks strange. Is this something I need to be concerned about? Is there a way to pull out or examine the reads that constitute this extra peak? I also noticed that the kmer profile has changed after trimming especially in the 3' end.