Sleepy Joe, my 1st indoor grow!

Hi, i'm no Plagron specialist, i' m using Biobizz, but I think you got all you need. Your problem looks to me more and more like a Mg defiency and since you got it and also the other probably lacking nutrients in your soil and fertilizer, it might be the cause that the plants cannot get it inside. That is often caused by a bad/ too high pH. All the nice nutrients cannot enter when it's too high. If I was you I'd rather get a pH pen and pH-down and adjust it. Trichoderma and mycorrhizae help to get the nutrients inside the plant. I hope it helps

Topping is okay at that spots where you placed the knife. You're not using fertilizer at all, so over-fertilization won't be the cause. I think it's rather a lack of nutrients, could be Mg, Ca or P in this case, hard to tell. You better use Plagron's basic NPK fertilizer! A pH pen and correction to 6.2 would be nice for your plants if possible. Are you using microbes, trichoderma and mycorrhiza?If not, do it to prevent such lacks! 🍀🍀🍀

Ready for topping?