My NHR died the beginning of this year. After reading and reading threads and posts. I believe she died from EYP. All sya proms were the same. Except I did not catch the water belly. I am the same way worrying about every little hint!
They do not always have the bloat, though. Some of mine never bloated at all, just began losing weight, quit laying and became progressively weak. Upon internal post-mortem examination, they'd have masses of cheesy mess inside of them, but you often couldn't feel it from the outside. So, don't beat yourself up about missing signs. There may not have been many. The first hen I had who died from EYP had no signs, just was lethargic one day, sitting in the shade on a cold day, which alerted me. I picked her up, examined her and could find nothing wrong. Next day, she was just gone, loose yolk all in her abdomen when we looked in there.