whats causing this yellowing to my flowering plant?

It seems like the leafs at the very bottom are turning very yellow my plant vegged for two weeks then flowered after that so she is 7 weeks old in total.. just want to know why the leafs at the very bottom turn yellow please help!!

heres a pic please can anyone help???

Normal. Its using up its stored energy to make those przed nugs. Keep doin what ur doin and get ready cause the finale is about to start u should start seeing some cool ass colors comin off those leaves soon. But as long as it stays uniform like that ur good keep er fed and watch her change

It's using up the nitrogen in those leaves.
A lot of people start using flowering nutes when they go 12/12,
when in fact you should keep up the veg nutes for several weeks after going 12/12.
They have a huge growth spurt and use up all of the nitrogen which is a mobile nutrient, meaning the plant can take it from the least used leaves and move it to where it's needed.