Tomato plant was doing great in new window garden (version one) for about 2-3 weeks – but then small brown spots started appearing in the central part of a couple of leaves. The brown spots, although still quite small and only appearing on less than 20% of leaves –  seem to be rotting straight through – perforating the leaf. The veins in the leaves also seem to stand out more in the affected ones.

Has anyone seen this issue before or have any ideas?

Thanks!