My indoor basil plant has developed some scarring and has some pretty deformed leaves. Could it be due to the caterpillar that chewed up quite a few leaves a few weeks ago, or is something else the matter? The undersides of the leaves look healthy.
These plants may be getting too much heat from the window. I would try moving them to a shaded spot and allow a couple hour of sunlight a day. When leaves turn under, it's usually a sign of heat stress. Even though the plant may be getting ample moisture it's still suffering some heat shock I think.