It sounds like you're dealing with some issues with your plant's leaves turning yellow after the stretch phase. Let's see if we can troubleshoot this.
Since you're using BioBizz soil mix and avoiding additional nitrogen due to concerns about burns, it's possible that your plants might be experiencing a nitrogen deficiency. Organic soil mixes like BioBizz usually contain some nutrients, but they can be depleted over time, especially during the flowering stage when plants have higher nutrient demands.
Yellowing leaves can be a sign of nutrient deficiencies, so it might be worth considering a gentle nitrogen supplement. You can try using organic nitrogen sources like fish emulsion or blood meal, which can provide a slow-release form of nitrogen without risking burns.
Additionally, since you're using Terra Aquatica nutrients alongside BioBizz, make sure you're not overfeeding your plants. Too much fertilizer can cause nutrient imbalances and lead to issues like nutrient lockout or nutrient burn.
Another thing to consider is your watering routine. Make sure you're watering your plants properly and not letting the soil become too dry or waterlogged. Inconsistent watering can also contribute to nutrient uptake problems.
Lastly, check for any signs of pests or diseases that might be affecting your plants. Pests like spider mites or diseases like powdery mildew can stress your plants and cause yellowing leaves.
By carefully assessing these factors and making adjustments as needed, you should be able to address the yellowing leaf issue and keep your Gorilla Zkittlez Auto thriving. Good luck!