im going to give her the first feeding on week 2 ,actually i already flushed with new R/O water
flushed after two weeks ? two weeks after germination ? if yes, then it is normal that you get N defficiency: flushing removes nutrients from soil. Flushing solution even remove them inside the plants, replacing the nutrients by empty chelates.
NEVER flush before the last two weeks. People who do it before are either experienced growers using non organic stuff (organic requires much less flushing at the end) , or people who know that they made a bad mistake in the soil and they try to fix it. Generally, people do not advise to flush at early stages, this is high stress on the plant and it is a signal to the plant that it is the end for them: in response to this they produce resins, and if it is too long, they have great chances at becoming hermaphrodites, because it is its survival technic in a stressful environment like the one you are creating for your plants
Especially autos, there is not much to do to fix stuff if you have made a mistake.
With young plants, it is enough to "drain" (water until water comes out of the pot bottom), but I don't think it is ever necessary to flush before the end, except if you are trying to fix a previous excess of nutrients or acidity or something like that that cannot be fixed otherwise.
Now, you must put your nutrients again, but as you have already watered when flushing, you may have to wait for the pot to dry. You can also divide your dose of grow by 2 or 3 and spray it over the yellow leaves, rather than watering the soil again. Or re-water now and put a fan toward that pot so it dries faster.
Anyway, water or spray, use only a few xrops of Grow (see xhat your nutrient maker says) and it can take 7 / 10 days to re-greeen. Also, autos do not like N the first few weeks. Use less than 1 ml per liter if you have to use it.
Or may be I did not understand your post, but from my experience, if I understood your post, yes, you did a big mess ;-) No worries, it's the learning curve
Autos can be delicate.
Good luck !