Black specks appearing throughout starter
I fed my stiff (50% hydration) starter a large dilution last night, and then this morning noticed black specks appearing right through the dough. Concerned, I clipped off a tiny piece from a previously formed rising loaf and seeded a second container of starter. I examined the second one as I mixed it in, observing that the container was new and by the end of mixing the starter had no black spots. Both starters sat out on the counter in closed plastic boxes for the day.
Now at the end of the day, BOTH starters have black flecks through them, even though the second one definitely started the day with none. Should I be concerned? What would cause this? Is this starter still safe to make bread with? The flour? The water? We already baked and ate the loaf from which I clipped a piece for the second starter within 3 hours of baking, while it was still cooling down..
Sad to think I might be looking on the last days of a starter that has served me for months..