I've flushed plants for about 20 minutes with a shower handle during the last weeks before harvest, no prob.
I bet you could flush them quite easily for an hour, they get even worse than that thrown at them in nature, it becomes a problem when it happens too often.
I'm sure you could rinse the soil till its neutral?

5 PH isn't any where lethal as far as I know, just not very healthy for them. The damage your plants took in the pics will probably only slow their growth a week, 10 days, I would think, and effect some yield. But I've never had it happen to me, so its only speculation.