What’s the cause on nute burn during flush????

I thoroughly soak in this case soil in my bathtub until the medium is completely saturated and runs off plenty probably more than necessary at least 25% runoff maybe closer to 50%

What’s your flushing technique? Are you soaking the substrate, letting it sit for 10-15 minutes, then coming back and running 4-5x more total volume of water through it? It could be you are doing the first step...that would leach the nutrients out of soil but not flush them out, allowing them to come and remain in contact with the roots and cause nutrient burn etc.

WOW..you've got me there mate! I've never heard of that EVER!!! have you been top-dressing? the reason i ask, I read an article in soft secrets a while a go about this guy who reverted to dry amendments from bottled nutes..he was top dressing every 3/4 wks and watering in as normal. About 10wks into flower he went to water and they were all limp and on deaths door., he lost all 5 plants due to over fertilisation, toxicity. He couldn't work out why. every time he top dressed then watered in, he put the water in that fast some of the of the essential nutes floated and remained on the surface of the plant, he did this for them full 10 weeks, so imagine when all them nutes on the surface eventually hit the root ball!!!! it was game over..if using dry amendments and top dressing check out mr canuks grow (matt) he explains organic growing and dry amendments to an art form