Light burn?

Hi there Tckfui, this looks like calmag deficiency you're right. this you can see from the newer growth being affected first and the fact you have been adding a bit more in the spray than usual. You know that absorption rates in the leafs are 80% efficient compared with absorption in the roots which is only 20% efficient. so it became a (pretty rare but possible) Mg lockout. If you can try to flush, go for it. water until runoff, then add 20% more water. Then skip Mg for one or two waterings and add it back again. Some genetics or phenotypes are just a little more sensitive than others , that's all. hope this helps ! 🚀