how long does your organic soil say it should feed the plants till? You could prob get away with using a very weak vegging nutes....and just make sure your water has been pH corrected. Did you add dolomite lime to your soil? I mean they look healthy but as you say the left one is turning slightly yellow which means nitrogen defficiency. If your soil has added nutes then maybe its a pH problem of the soil? so dont panic and do sometrhing you will regret but just be cautious. If you do decide to give a vegging feed then make sure its weak, like 1/4 strength at most, and see what happens