I agree, it's looking like overwatering, and slight overnute.

Working with five gallon buckets, you need a few adjustments.
1) Adaquate drainage/airflow ports. This means holes in bottom and sides to allow moisture escape, and increases airflow to roots.

2) You need enough soil in the pot, that the air above the soil won't sit stagnant. Fill to within a couple of inches from top, leaving just enough room to allow adaquate watering.

3) In five gallon buckets, you have to adjust watering, because the soil near the bottom will remain moist for what seems like forever. If you are not allowing that soil to dry between waterings/feedings, you risk lockout and root damage. (root rot) Fill a bucket with soil, and a half-gallon of water, and see how heavy it feels. This will give you a general idea on how light the pots should feel before adding water. The 'brownie toothpick' method for checking soil moisture by sticking your finger in, doesn't work with that type of pot.