1st Grow Ever. Gary the Grapefruit Auto

Accidental leaf burn from careless low humidity/light intensity when relocating space bucket to new area in house. Primarily on lower leaves and on one side of the plant. Changed to lower wattage lights this week as previous lights were suspected to be too powerful for application. FIM on 2.16 at 6th node. Dark foliage w clawing still. N tox? P def? High light intensity? .75gal big bloom soln 2.17 Very thick central stem with very little inter-nodal spacing.