Leaf tips show a nutritional Maybe Ca deficiency and nutrient flush timing

flushing is something to avoid not incorporate into a normal process. you inevitably strip away a lot more than whatever the problem is don't think it's ca related, and the fact you've been adding 'some' makes it less likely too... does it add up to ~100 elemental ppm or more? If so, it's very unlikely Ca-deficiency. This is the great thing about soilless growing. Since you add all nutrients, it's easy to learn where your upper and lower thresholds are for elemental ppm. Elemental ppm is more accurate than a TDS pen converting EC to ppm. The fact there are 3 or 4 different conversion factors to do so tells you how inaccurate those TDS pens are at giving a ppm value. EC is accurate, but it can be converted 1 of several ways all of which will tell you a wildly different PPM value, lol. You are 7 wweeks into flower and have good ripening of calyxes. I wouldn't change much and definitely don't do anything drastic like stripping all the nutrients from your substrate with a flush. That'll just make things worse. Free apps and web pages can calculate elemental ppm from your gauranteed analysis labels. N 80-100 P 40-60 K 180-200 Ca 100+ Mg 75ish S 100+ If anything is drastically off those ppms, it's your likely culprit - directly or indirectly (inhibited due to competition of something too high). no guessing like with soil. take advantage. keep notes on this stuff over time as feeding is about cumulaative behaviour from the beginning and not just last night or last week.