dont know about nute burn, but i see your temp and humidity is not adjusted for proper VPD for flower, according to calculations made by Northern Loki (dont want to spam with mentions) on this thread:
for humidity of 50% you need temps from 70 to 77 F, if she is really trying to retain humidity (if she is loosing it too much), then that might be your solution, but then again, it should show on other ones also, so i would check about nutes, maybe post pics of other ones also so pros here can inspect…