I've done evil things to E6 chemistry but never had the issue you report here. Yes, films spit out all kinds of strong color when I prewash them, never caused any problems in the end results as far as I can tell. The "very red" you report would indicate either a light leak somewhere (camera, film tank) or a severe case of fogging from old age. I once developed 20 year old poorly stored E6 film and it came out with a strong red Dmin.