If you examine the frame where the horizon has fallen into the sea, could it be that, instead, the emulsion has slipped on the base? If so, you probably had bits of emulsion (still with their color dyes) floating loose in one of the later baths (after color developer, for certain) that might have redeposited, leaving the blue and green blots on the other frames you posted.
The most likely causes of this are baths too hot (100F is what I recall for E-6) or something mixed wrong that's softening the emulsion far more than just being wet normally does.