It is strange that it happened. I used just a weak mix of the most famous washing up liquid, as I always do. But this time it just blackened and damaged a lot of leaves. I did it in quite a hot period of the afternoon, so could that have had a different effect to normal. Anyway, the upshot is that they survive and look to be in good health.
It could be that you just provided a bigger squirt of washing up liquid than usual.
Might be worth checking the bottle does it say it’s new and improved??
My wife had used a specific hair dye for years then used the “new & improved” version and had an allergic reaction as a result! Brands change formulas without one knowing exactly what adjustments have been made. In these times of high living costs the manufacturer may have switched to a cheaper ingredient. Good to know they survived!