[Wasserpest]

Nice start. A couple of things that jump out...

- Your water is very hard. You are adding GH booster. Your plants are what I would consider typical soft water plants (even if some manage to get them to grow in medium hard water). I think there is your first problem.

- You are adding 1/4 tsp N and 1/8 tsp P. I must be old school, I always add N in a roughly 10:1 ratio. So I think something could be off, be it too much P or too little N. Have you tested your tap water and your tank water for these nutrients? I know with spooning in stuff supposedly you don't need to test, but it does help in the beginning to get a good grasp on the dynamics in your specific tank. In some places there is a lot of P in the tap water, in others none. Also think about K, some tanks can be deficient in that as well.

- Related to that, what is your water change regimen? 50% a week I assume?

- Have you checked your CO2 levels? This is a big one for more demanding plants. "7.2 to 7.8" is a huge swing. If it is 7.8 then with your kH you have basically not added any CO2.

Ok, this should get you started... :wink:

 

[Wasserpest]

Turning white could be a sign of missing N, but since you are adding almost 20 ppm every week most likely that's not it. IME "soft water" plants don't do well in hard water, unless everything is in excess. Looks like you are adding enough micros, however, in hard water (with often related higher pH), some of them like Fe and Mn are not as plant available.

Perhaps consider changing out your plants. That way you don't have to go to extremes to provide them with softest water. If you are not hard set on specific ones, there are many that will do well in hard water.

 

[Wasserpest]

Looks like you don't need to add any more P, and can perhaps cut the N dose in half for now.

Using distilled water mixed with say 25% tap water will work, but you will have to do this very consistently. With 50% weekly water changes this can get old/expensive.

Let us know how things develop!