yellow leaf tips.

Hello ganzigunnu, I know what the problem is here and I had this thing often when growing with Biotabs. This is not light stress but nutrient burn. This symptom is often mistaken for light stress. You can tell the difference really easy because when the plants got light stress the yellow tips only appear on leaves close to the light. With nutrient burn, the tips are usually brown and appear all over the plant. I can see that your plant got burned tips on every node and not just the ones close to the light. You probably overfed a bit with the Orgatrex and the Bactex. Be carefull with the Bactrex. It is really strong and overfeeding with Bactrex is very easy. Read the back of the packaging and it will tell you the same. You can water with hand for 1 time and water till 10% runoff. Let the top 2 inches of the soil dry out. After you can start using the Blumat again and continue like you did before. I also experienced a lot of pH problems during my grows with Biotabs. This problem was solved when I started to use the organic pH min adjuster from Biobizz. It will not harm the bacteria and fungi inside the soil!!! Enjoy your grow!