Question regarding Worm Castings and Color Change.

I'm new to growing marijuana. I grow in soil and use HPS lighting. I have a few plants at about 6 weeks growing right now. I recently added earth worm castings to my plants. Gave each one the same amount, maybe the size of a seed cup or shot glass. The castings were laid just under top soil. They have been getting the same amount of light, water and air for the entire 6 weeks. After I added the worm castings, the plant changed from a dark normal green to a light yellowish green a few days after adding the castings. Nothing wrong with the plant still looks strong and healthy. I take that this is the (nitrogen?) from the castings. I know the plant color will change back to a darker green sooner or later. Looking to find out if there is a better way to add castings to a plant, so they don't change color?

castings have only a small amount of nitrogen in them, and the plants should not turn a lighter green after adding them. have you checked the ph of your soil, or taken measures to ensure the neutrality of the medium such as adding dolomite lime to it when you mixed it? nitrogen is a mobile element, meaning it can travel from one part of the plant to another part where it is needed more. after checking your ph, if it is within tolerance then you should probably give it a dose of some fertilizer, but without pictures of the leaves i cannot tell you if you are having a nitrogen deficiency or some other nutrient is lacking. usually, a very dark green plant is a sign of nitrogen overabundance, but not to the point of burning....

if you were previously feeding with a chemical fertilizer it would impede the usefulness of the worm castings. regardless.... worm castings have typically a slow release of nitrogen unless used in large quantities /30-40% of the soils make-up(found a lot in organic soil systems). You're plants may be starving, but it's hard to say.. what are you're ph levels like?? more info please.

BTW a shot glass worth of worm castings is like trying to live off of 4 carrots every day. its just not enough juice