Like described in the thread you may characterise your amplifier:
sweep across the frequency range of the LNA with a defined constant input amplitude to see the real amplification of the amp instead of assuming it,
make a high resolution FFT to see if 50Hz couples to strong in the LNA and that way artificially increases your noise when viewed with the oscilloscope,
test a few different noise sources to do a sanity-check: different voltage references like a LM399/REF102/ADR445/LTC6655, batteries, short
Only that way you will truly know your LNA and can actually reliably work with it. Otherwise you will doubt the results and it may have problems you dont know about.
Only a guess: did you use a dual channel ADA4528-2 or single channel ADA4528-1 and maybe now see intermodulation-related errors?