3 different dongles same freq range and samplerate

i have 3 different dongles
top = limesdr-mini
middle = r820t2
bottom = e4000
all are running “qspectrumanalyzer” (three instances at same time) coming off a splitter connected to a lnbf.
anyhow the samplerate for limesdr-mini = 2.5msps and the r820t2 and e4000 have samplerate 2.56msps.
why is there a large difference below 1ghz for lime-mini?
is something not working correct on limesdr-mini?