Tell that to nature.look like nute burn.
Also you should not have 2 plants in the same pot. why? because their will join roots and start stealing nuts and energy from each other untill the one with stronger genetics eats the other + stunted growth.
yes if they both have space.. outdoor plants i.e can get roots over 10-20 meters straight down. but im sure that 10 L pot wont be a problem youre right.Tell that to nature.
Plants can naturally grow if they both have space for two root systems. That's all. As for 'stealing' the plants will share nutes.