Formula 1 yellowing fan leaves

[Crowkill89]

Hi everyone, I’m growing two f1 autos by dr ray, they are 6 weeks old around 3 week into flower, Growing In biobizz light mix, 7.5l pots, using biobizz nutes, ph 6.2 to 6.3, the older fan leaves started going yellow and slowing dying off, also noticed some browns spot on some other leaves but not much, I’m working off the biobizz feed chart and using the 42 fast buds feed chart specifically designed for autos (will be picture up) my last feed was (per litre) 0.7 grow, 0.7 bloom, 0.2 cal mag and 0.4 acti Vera, around 500/600 ppm, the feeds for before this were weaker, I feed twice and then a plain ph water no run off but all feeds will fill the pot, 1.5l/ 2l every time every 3 days roughly when they dry out, can you look at the photos and try to see what my problem is thank you. I’m not sure my starving them of something any help appreciated!