HELP! Leaves yellowing/ browning and stems reddening

[PleaseHelpMyPlant]

I'm a first time grower, my plants are in the 4th week of the 18 hour light cycle. I first noticed the lower leaves yellowing and some stems turning red. I tried fox farms microbe brew and just switched them into a larger pot 2 days ago (3 days after the problem was noticable) my plant still seems to be getting worse. I raised the lights a few inches . I generally water them every other day but I did notice this morning that there's water build up in the tray under the sick plant.

 

[9fingerleafs]

They're not happy with the soil they're in. Also the roots may not be getting oxygen if the holes in the bottom of the pots are covered by water.

 

[OldManGrower]

you need larger pots, and a "spacer " between the pot and the runoff dish so that the plants do not sit in runoff. your ph is out of wack and needs adjusting as well as adding some cal-mag to your feeding schedule.