Nute Burn

My Plants got Nute Burn, the tips of the fan-leafes start to be burnt, some more some less. The sugar-leafes start to get yellow , I guess cuz of too much nutes they no longer get what they need.
Is there any way to find out what my plants got too much of ? or is there only way to flush and start all over again with a little bit less of each ( using biobizz grow, bloom, topmax).
They are in week 8/9, growing in coco. If anyone else is using biobizz with coco how much do you use ?

cant help u with coco , but with theire all mix soil start feeding at 50% only on week 4 , and then on week 5 100% , if u do nuts a before week 4 u will get nitrogen toxicity and other burns , but i only discovered this by my self not looking at theire charts that induce u to give nuts earlier