SO Blueberry

@grumbledog74 Hi there! If your plant tends to be lime green or pale all over, even though the leaves appear healthy without stripes or spots, then it's a Nitrogen deficiency. If your leaves are clawed and have a deep dark green, then it's a Nitrogen abuse/burn. If your issue only concerns the highest leaves, then it could be a light-burn. If your issue only concerns the new growth, then it could be an Iron deficiency. From what I see in your last pictures, this looks more like a deficiency. In every scenario, wrong pH can be involved. I'd recommend to re-calibrate your tools and double check your pH. Hope this helps, keep us up-to-date so we can help you in parameters adjustments, and happy growing! 👊

Oh and I forgot to mention : those QBs are known to be over-effective onto young plants, what's your dimmer setting? At this stage you should be running your board at 25% / 30% max in order to avoid light-stress.