Yellowing

I see you're using BIobizz, if it's a light mix, that's your issue. I've done the same on my Ztrawberry plant. And it needs PH'ed to 6. It helps the plant break down the feed. Also the spots. You need cal powder from GHF. As they suggest that's needed. Especially if your tap is less than 200ppm cal powder will be needed. They do say, if you use. Its recommended you start of with a soil that has nutes in it. As biobizz light mix consists of 70% coco/perlite and the rest, (therefore, a lower PH is needed). As there's more than enough nutrients in biobloom for 8-10 weeks. So, its not lack of N. You're right, it'll be more of a PH issue.