Brown streaks down the front of two hives in mid-September — dysentery or nosema, and what can I do without fumagillin?

Fifth year in Małopolskie, ten hives. After a warm start to the month we've had ten days of cold rain and the bees have been stuck inside. Two of the ten hives now have brown-yellow streaks below the entrance and on the landing board, and there's a sour smell when you get close. The other eight are clean. Some things about those two: they're in the shadiest corner of the apiary right on the forest edge. One of them got a batch of syrup three weeks ago that had a faint yeasty smell — I used it anyway, which I already regret. And both brought in a lot of fir honeydew this summer that I left in the brood boxes as winter stores. Is this nosema? I don't own a microscope. There's no fumagillin in the EU and I keep reading that nothing else actually works. What do I do this autumn, and what should I stop doing?