Do you mean Feb-March 2017 or 2018?
If you mean 2017, then yes, actually there was a pretty substantial change: we released MSigDB v6.1 in October 2017. MSigDB v6.0 came out Feb 2017, which is right in that timeframe. So if that's what you meant then it might be worthwhile to go back and re-run against the MSigDB v6.0 files to see if there's a difference. I don't *think* the Hallmarks collection changed much, though, so it seems unlikely in any case.
If you meant 2018, then nothing should have changed on our end since then.
If you're working on the same computer, you might try going through the GSEA history directory to find your old analysis for comparison. Use "Help > Show GSEA home folder" and then look in 'output' for the correct day. There should be an RPT file with the analysis settings, etc. that could be useful.
Regards,
David