Need more info r u in soil or gyrdo? what do u feed with. and how often? from just a pic. looks nuts.burn from bad ph if its hydro look at roots r they milky and slimy? if so its could be heat. I say do nothing till you post all info needed so someone can pinpoint the problem. the last thing you want to do is try several different thing at once and the gets fixed but you dont know for sure what one it was. for your own ref. if you run into the same thing again. ps.paint the walls flat white your wasting light that your plant needs