Since you are not growing in soil I would say that your problem is from a high tds. I say this as your leaves are curling, burning(browning) and algae is growing off the excess nitrogen on the perlite. Cut the tds in half at least and you should be fine. If you were growing soil I mix my nutes to 5.9-6.1. Your tips are not burnig so I wonder did you just up the tds? What nutes are you using?
One love
c