Bottom Fan leaves start to turning yellow , need advices.

Hello everybody , I have 2 plants which are 4 weeks old. Three days ago I started to 12/12 light schedule for flowering stage.
But I realise bottom fan leaves turning yellow.I 'm using Hesi Soil fertilizier set my grow.Ph seems normal 6.7.
Also I grow this babies on my balcony with sunlight.

Please check my pictures and please tell me what you think .
Peace
.

you can add a little more nitrogen but seeing as how your already in 12/12 i wouldnt worry about it, leaves die. as long as its just 1 or 2 leaves a week (at worst) then your ok. overall the plants looks fine

Thanks Nick for quick reply.
Also I would like know , am I put them under sunlight directly ? Does it hurt my plants ?
They are around 15 inches now in 3-4 liters pots ,I can transplant them bigger pots but ı don't want too much bigger or higher plants.
I think they are going double size in flowering period ,am I right ?.
Peace

The leaf on pic one is yellow cos it's amongst dense vegetation with no light reaching it.