Yes that is Nute burn. If you would like to know if, how, and when to deal with it more info is needed. The more info you supply the better information you will be given. Good Luck!
Soil is FFOF with added dolomite like (2 tbl per gallon) and Jamaican bat guano (1 tbl per gallon).
Nutes: earth juice grow bloom and catalyst
pH of soil is unknown and I don't check the pH when watering. I just bubble for 24-48 hours and then feed. Feeding schedule is water water feed.
Temp 68-79 F
Hum 50%
Im assuming that I fed it too much because I was using 1 tbl of both grow and bloom the first week of flower. My guess was to just feed water for awhile so it can fix itself.