Ideally (or you simply need to) add calcium-magnesium supplement to your feed. Consider foliar application - quicker results and doesn't add salts to your feed water or media/soil. I use CALiMAGic, a cal-mag supplement with lower N than many others. In the meantime, with no N or other significant excesses readily visible, consider feeding at a higher base nutes dosage to increase your Ca levels (presuming your base nutes include Ca).
Don't totally stop feeding because you see a deficiency! Unless you are in soil (what media are you using?), it is best not to feed pure water; rather feed diluted base nutrient (along with some cal-mag). Looking at the leaves and with this being in early bloom, you may even want to ramp up feeding in general.
You will want to pay attention to new growth. The existing leaves will not improve their color. They are still for the most part working and also storing nutes and fluid, so don't remove them other than the worst damaged. If some sickly leaves are blocking light to healthy leaves below, consider removing them. For ex., in the picture, I'd just remove the center most damaged leaf.
[Get other opinions about supplementation, feeding and defoliation].
