The dark specks were definitely not there when the dough went into the fridge, and I've never seen this before on matzo balls or rolls except when black pepper has been used (it wasn't here).
Due to a situation, I had to let my passover matzo roll 'dough' sit for about 6 hours in the fridge (rather than the required 1 hour) before baking.
Undoubtedly, the egg whites fell somewhat, and the rolls will come out dense, which isn't optimal but will suit those who are happy to have a bread alternative.
Only ingredients are water, oil, salt, sugar, matzo meal & eggs, the latter separated & with beaten whites folded in.
You deserve a cookie.