Your plant uses such small amounts of sulfur, that its not going to do anything unless you have an obvious def.
It looks to me like your plants need water or they arnt adjusted to the bright light of the sun.
Cut a little hole near the bottom of your planter or stick your finger up one of the drainage holes in the bottom of the plant and see if its really wet, dry, or just right.
To me, it looks like your plant is slightly def in N and/or minerals, under or over watered, and/or unadjusted to the brightness of the sun.
If you have the option, plant them in the earth with some worm castings, bone meal, and kelp meal.