Nute burn or pH Flux

Looks more like mechanical damage to me, from the leaves hitting the edge of the pot when the fan is blowing on them, most probably at night when the plant has lowered its leaves to the "resting" position. The lowest leaves going yellow are due to being in too much shade. Both these things are fairly normal occurrences and do not need any remedies. Your plant will grow normally, there will be no yield losses or potency reductions caused by either of these two things. The uber faint yellow tips can be a sign of impending nitrogen excess. Make sure to water until run off each time, this will help prevent nutrient salts from building up to toxic levels in your substrate and causing any issues or burning. Hope this helps,........ Organoman.