...yeah man, that MG soil is problematic at best! it explains the tip roasting, even at the mild fert' regime you've used,... problem is, which nute, or nutes, are in excess and causing the burn,...pH plays a huge role in this too, BTW,... I'm just making an educated guess, but likely with that soil, it's too acidic,...the tips-- has damage progressed, or is that older, now stopped? See, it's difficult to make a solid recommendation on what to do without the right info, mate,... if pH is off enough to interfere with absorption, adding nute's to treat defc. may be pointless, even damaging,... if the tip damage is older, and stopped progressing, upping the nute's a bit may help if there's a K defc. issue, but that's not certain,... fortunately, all symptoms are mild now, and sometimes they have to advance some in order to show specific diagnostic clues,... So, try getting some dedicated Ca-Mg supp's, or even molasses would be okay; it has Ca, Mg and even some K in it so it'll cover the bases for now,... plus the sugars will make the soil herd happy, making the plant happy in turn!.... treat at 1tsp/qt,.... epsoms don't have Ca in them, it MgSO4 only,.... good stuff, and I wouldn't hurt to add some anyway, as it's often at this stage that plants develope Ca-Mg defc. issues,... same dosage too,...
