Anyone know what this condition would be on this paddle plant leaf??
If that's some / one of the lower leaves, it could be on its way out naturally, as the plant grows it sheds the lower ones.
OTOH, your soil looks way too rich for this plant - too water-retentive. I'd cut your soil with 50% perlite/similar material and repot it in the more porous mix. If you can show us a picture of the whole plant, it would be easier to say for sure.
It that the variegated one? They're more prone to problems, particularly if they're tissue-cultured.