Whats wrong here?

either K excess and Ca lockout or just Ca deficiency (if u're not usining water with Ca or Ca fert at all)

it looks like nitrogen lock out....

Agreed… you have a lock out. Try to raise ph level. If this does not work, then you need to flush your soil with around 10 times the volume of your bucket, and add nutrients carefully… but usually she bounces back if you adjust PH lvl. Enjoy the grow 👊🤞🏽🍀

your PH is to low, get that kicking around 6.2-6.5 and it should bounce back. Likely locking out some micros and causing the discoloration. Soil does a pretty good job of managing its own PH using the microbes that grow in it naturally. If your altering your PH going in to 5.66 stop. if your monitoring your PH of the soil using slurry test you can boost it back up with Lime or PH up. If this is the run off PH, soil should not be getting runoff, best to feed water water, little to no runoff. less is more.

5.66 is very acidic, tips are what I'd expect from 1.8 ec. Reason why it skewed to acid? You yourself should have a better idea of what you have been feeding, ph isn't just a number it's a indication of the ratio of cations to anions in soil. 5.66 means there are more acidic atoms. Now if you know you have feeding of lots of calmag for example it's highly unlikely it's a nutrient based problem with such a skew. On the other hand you have t fed her any calmag at all I'd expect 5.66 ph eventually. But other things can make your soil ph skew, hypoxia for example(low oxygen conditions) in soil can contribute to a shift in soil pH towards acidity. This occurs because anaerobic microbial activity, which increases under hypoxia, produces acids as byproducts of respiration and decomposition. Additionally, the shift from aerobic to anaerobic respiration in plants and microbes can also lead to the production of acidic compounds. Pretty common in flower as soil generally becomes more moisture retaining as flower progresses. If there is no negative pressure applied oxygen won't be forced in and out of your medium. This is why I can never suggest running high rh, especially in flower indoors, it may be best for vpd , but that's what's best for growth outdoors, is not whayts best indoors, nearly every guide out there tells you to run high rh Yada Yada but Unless you have a solid understanding of the entire cycle of how wayer moves from one atmosphere to another and have the correct setup to deal with the high levels of moisture appropriately then your grows will always be at the mercy of hypoxia or some bottleneck to do with spac.

The brown/rust-colored spots often indicate a nutrient problem - in this case probably a so-called lockout. The EC value of 1.8 is relatively high for cultivation in soil in my opinion, but should not be the problem - in combination with a pH value of 5.66, the pH is well below the optimum range for soil (6.0-7.0). As a result, important nutrients such as calcium, magnesium and phosphorus can only be absorbed by the plant to a limited extent or not at all - even if they are sufficiently present in the medium. The plant then shows classic deficiency symptoms, although technically there is no deficiency. feed a light balanced nutrient mix at proper pH (6.3) It is easier to give more nutrients than to take some away. Have fun and good luck 🦖

5.66 ph is wrong for soil, range is 6.2-6.8 , in reality better keep 6.3-6.5. Ec is insanely high too. By burn place, would say its immobile or micro nutes that you overfed or they became unavailable because of wrong ph range.