yes your correct its best not to have plants in the same container fighting for room and nutes, whats done is done

& divestoned I agree with also, the plant on the right is possibly needing more sulphur or iron hard to tell at this stage

you can foliar spray the plant on the right with epsom salts (magnesium sulphate 13% sulphur) this is only a quick fix tho
you may have ph issues starting or your nutes may not contain micro nutes.... iron, sulphur, magnesium, copper etc. etc. etc. check your ferts label

to be safe & rule out any ph related issues complete a soil runoff PH test.......
with PH corrected water (6.5-6.8PH ) pour enough water in the pots so the water runs out the bottom of the pot ...collect & test the PH of this runoff water....