Indoor Live soil cob grow please help

[Blalack55]

Hey guys I'm starting to get a deficiency in the live soil grow from what I've read its worth mag or potassium i think because the older fan leaves are turning yellow but not dying and drying out you can see in the 2 pics

 

[Blalack55]

@Slater do you or anyone you might recommend that I can use maybe from home depot or lowes? I don't want to buy the wrong stuff or you know anything I can use that I can order online? I can't buy a whole lineup of nutes, I'm limited to stuff I can get locally