Excessive fertilization can cause burns starting at the leaf tips or edges especially if salts are used to fertilize can cause salinized soil/substrate causing problems with osmosis. With osmotic problems, the leaf edges also can curl up (high tension) or down (low tension) before they become necrotic. This can be determined by flushing the soil with clean water with a low EC and collecting this water and measuring its EC value again if it has a higher EC value then it might be you have salinized soil. Then keep flushing till it stabilises or replace it. If it's OK you can rule this cause out.
But usually, non-infectious necrosis is caused by a combination of unfavourable factors for the plant in situ that also can be atmospheric such as temperatures, humidity, drafts, and location.
Plants can be pretty sensitive to sudden changes in the climate that we are unaware of. I experienced plants doing very well in this corner of the house and the same plants suffer when placed in a different corner. So it kinda looks like even in the same room each corner of the room has its own typical microclimate bubble which is about unmeasurable for us.
Another example, I placed a hygrometer 1 inch above the water line of my open-top tank. And it constantly measured 45% humidity with the lights on. Meanwhile, a hygrometer placed in the room the tank was in showed 70% humidity and outdoors, it was even higher. With some straightforward logic one would think 1 inch above the waterline the air humidity should be the highest, but somehow, probably temperature and air density and air speed rising caused by the warmth of the lights have a saying in this too. It's never a constant and always a sum of factors. This makes it pretty darn difficult to determine the exact cause. And also difficult to determine how nature exactly works, physics in nature isn't exact but rather very dynamic.
I had the same issue with a large emersed growing Echinodorus in an open-top tank. All older leaves suddenly start drying out their leaf tips, while the same plant growing outdoors did this at a much slower pace and stayed healthy for longer time. Older leaves will die one day and be replaced by new ones which are pretty normal. It's just not us that determines the age of the leaf and when it's time to die. This is something the plant regulates. With a fast-growing plant such as Echinodorus, it is something to learn to live with and cut the old leaf off, slow-growing plants will never grow to their full potential and stay significantly smaller that way.
As you can see below, the old leaf closest to the water shows a burned tip.
