Yellow and burnt leaves......why?

[otg1sl]

I have a few plants that are in the 5th week of flowering and I'm using several 4ft t5 florescent lights. All are doing pretty well except two have issues.

The first plant (pic #1, 2, 3) has several leaves that are yellowing and toward the bottom of the plant a few leaves dried up and fell off........what are some possible causes of this?

The other plant (pic #4) had 2 or 3 leaves that looked like the ends were burnt and dried. The rest of the plant/leaves seem fine but was curious why the burned look at the end?

Thanks in advance for any input :smokin:

[olyippie]

looks like a nitrigen dose your nutes have a N-P-K with numbers the N is to low.I'm pretty sure...