I've had some problems with my NEIPAs coming out grassy, and have been trying to nail the problem down.
I've been brewing long enough to know, that a tiny change in water isn't going to cause this type of off flavor (or lack of bright fresh hop flavor). I correct my mash pH, but also don't believe that could cuase this problem. I'm prety careful with transferring to minimize 02 pickup, but again, you'd have to get pretty reckless to absolutely destroy hop flavor in a very short amount of time by using poor transferring techniques.
I moved a couple years ago, and haven't wired up a 220v outlet for my electric brewery, so I've been brewing 5 gallon batches, and just cooling in a water bath instead of using my immersion cooler. I'm pretty sure my grassy flavors were coming from extended steeping times at too high of a temperature. This last batch, I used my electric pot, and was going to use my IC, but at the last minute I was missing a fitting. I cooled the wort in ice water, and only let the steep hops be in the wort for about 20 mines, at 170F. I then made sure not to pour any excess hop material into the fermenters. On day 2 of fermentation I dry hopped. 1 bucket got only 2 oz of dry hops, the other got 6 oz, just trying to rule out the dry hop variable. I'm pretty sure dry hopping wasn't my problem, I have a lot of experience doing that with traditional IPAs and never had a problem, typically do 3 days around 60-68F, I use a bag.
I'll report back at bottling and tasting time to let everyone know how it goes.