What am i doing wrong? and what shall i do?

Just looked at your diary... it's just about at this point in every grow where these issues raise their heads. Transitioning into flower requires the nitrogen-heavy nutes to be reduced or they will lockout other important nutrients such as calcium... But I think this is going beyond (although including) calcium. Flowering plants also need more potassium and phosphorus right about now... and your plant is showing (along with a calcium deficiency), a deficiency in those two nutes as well. Here's what I would do .... even though you say you've done it twice, you need to flush your plants. This means running 3x the pot volume of pH'd water through each pot ... you don't tell us what size pot you're in but if, for example, you're growing in 3gal pots, you would need to run 9 gallons of pH'd water through each. In the last gallon, give them 1/2 strength nutes BUT only 1/4 strength of the Perfect Grow. You can also give 1/2 strength calmag, too. Now wait until they're completely dried out before giving them another drink of plain pH'd water. When they're dried out from that, give them 1/2 strength Perfect Grow and your normal dose of Perfect Micro and Perfect Bloom and a 1/2 strength dose of calmag... and don't, for the rest of the grow, increase that Perfect Grow at all. The calmag should only be given once a week but should continue throughout your grow. You might also want to consider adding in some PK booster such as General Hydroponics KoolBloom liquid... Good luck...

Calcium deficiency, or at least a PH issue leading to a calcium deficiency. This is what caused the brown spots on the leaves which will lead to large blocky brown dead bits. You said that you've flushed twice already - have you tried adding back in fresh nutrients and including CalMag in the feed? The discolouration on the leaves is not going to disappear now whatever you do, but it will get far worse if you don't feed them nutrients.

qui qualcosa che ti potrebbe aiutare...ho pensato subito al cal mag ,che è simile,ma non è quello https://www.royalqueenseeds.com/us/blog-leaf-septoria-yellow-leaf-spot-on-cannabis-plants-n678?_gl=1*1gw0dqm*_ga*Mzc5OTUyNzIwLjE2Njc4MzMwNjU.*_ga_MFLBPT8N0L*MTY3OTkxNjg0MC4xNi4xLjE2Nzk5MTY5MDUuMC4wLjA.