what is goin on with this plant? i just got new lights/more lights, and put up reflective surfaces, and watering it with a a very watered down nute/rooting solution. All my other plants love it but this one has the bottom leafs yellowing then dying two days later.

1st pic. yellowing leaf.
2nd- wierd spot.
3rd. another yellow leaf with burnt tips cut off
4th- top view of plant
5th- full grow room.

the 2 big ones are purple kush, left small is GDP, right small is purple urkel, and the burnt yellowing one is ??? . STINKY HELP PLEASE