One single plant with deficiency but all other are good?

[fishingBuds]

2 leaves of my amazon sword are having this issue while the rest of the plant and all other plants are okay...

20g tank:

Seachem flourish }
Seachem iron } all precise dosing
Seachem excell }
MINI co2 system (day)
Airstone (night)
Seachem root tabs
Aquaron rich substrate
Tetra 40g whisper filter (no carbon activated) so the filter is double the size and power

Plants without deficiencies:
Anacharis, hygrophilla, echonodorus, ludwigia

Plants with deficiencies:
2 leaves of my amazon sword only