BioBlazeanswered grow question a year ago It seems like a deficiency. Based on the given information I assume the plant is receiving too little nitrogen.
However I really cant tell for sure. It might also be too little Calcium & Magnesium.
Ask yourself these questions:
Is the water Im giving hard or soft? May research on google about water quality in the area.
Does the plant receive enough and the right amount NPK?
Take it from there....