Potassium issue?

Hi there Thracian, so basically it's still a magensium issue, you can see that from the discoloration on the serrated edges of the plant. Like i said above, a spray is much better. Uptake efficiency through the leafs is 80% and uptake efficiency through the roots is 20% so, it's a quicker way to fix deficiencies. Just make sure the water dropplets are quite dry after a while otherwise they can collect on the leafs and even make a burn like what you're seeing now because of the lights. otherwise just up the calmag a bit in the feed. Lack of cal mag is a very common problem in biotabs . That's because there is not enough regular chelation or something like that with biotabs. Everything else is fine growmie, just fix this and the problem should stop spreading immediately. Hope this helps ! 🚀