And.. phosphoric acid is commonly used in foods/beverages, but just watch it etch steel (even significantly diluted).. pickling.
I expect that the hydrochloric used in the process of making plumbers flux could be a contributing factor, but I'm no chemist.
It might be worthwhile to re-do the cable soon before any/all recollection is gone.
If the wires were heavier gage, they might last for years, but those fine strands in 28ga wire are fairly delicate depending upon the number of individual strands.
There are numerous methods for fanning out bundles of wires. In addition to making secure connections, stabilizing the splice area is very important with fine wires.
Roger on the piles of stinking corpses.. CSI will clean 'em up.