Nitrogen Deficiency and trying to fix it

So I just noticed about 3 days ago my bottom leaves are beginning to yellow. Is this a true Nitrogen deficiency? And what is the best option if curing it if so?

Yesterday I mixed some used coffee grounds in the soil and gave it some water. The ph of my soil is around 6.0 Was this a bad idea?

Coffee grounds hey. I find soil a bit voodoo like and try to avoid it but I'm now following this thread as I'm sure the crazy nutters out there would of thought of a far more extravagant way and I'm interested!

Science motherfucker.