I have three Influenza datasets from GEO (GSE34205, GSE48466, and GSE30723). Since each of the datasets have low number of control samples, I would like to put all control samples from all datasets into each other and use that against disease samples from each datasets separately. As I checked these datasets have the same platform and version. After doing so, the obtained p-value of fgsea increased which is undesirable. What can I do? Is there anything that I am doing wrongly?