different leaf issues

i looked through johnnyrex's post about his leaf issues and saw the link to that wonderful icmag forum with all the apparent plant problems, my issue is, i'm not sure which deficiency my plant has.. i have some pictures of one plant here.. the plant seems to be doing well for the most part but a few of the lower leaves are being affected and it's troubling me not knowing whats wrong.

i'm just basically growing for shits and giggles. i have 2 plants, only one is really affected, the other is showing signs of potentially the same problem however. the seeds i found in my carpet (haha i know, bad start) so the strain probably isn't the best. i'm using some miracle grow soil that was lying around for my ma's house plants (called organic choice, so i dunno whats been added to it already) and tap water (ph is normal).
i haven't added any ferts to it, as i'm poor and am doing this the cheap way.

my question is, what precisely is wrong. the icmag thread made it appear as though it could be one of numerous issues

any help would be appreciated, i'm a big noob as far as growing is concerned.

oh and it's not too old yet, if that's not already apparent by the pictures

that sure looks like a mold or fungus to me. Does it flake off? The brown spots one, looks like a mold that would flake off to me. If that's the case then I would be leaning towards humidity being the issue. If that is mold I would think you want to remove that from your grow space immediately.

The other plants look great. That sure is puzzling, when one does something and the others don't. Be careful it doesn't spread.

the entire leaf turns dry and flaky, if that's what you mean, but the brown spot itself doesn't flake off.
i cut off the couple affected leaves at the stem with a sterilized razor to be safe.. hopefully that will stop any spread..
the humidity is, if anything, too low. i keep a bowl of water in there for humidity but i guess ill try taking it out for a while.
it makes me wonder though, why only a couple leaves had this problem, yet the rest of the plant seems to be flourishing..

the plant looks quite good, overall ... it's perfectly normal for every plant to have blemishes, you won't grow a plant with 'zero bad leaves', it's natural ... your soil is OK, I've used that variety of MG successfully, (with more perlite added) ... resist over-watering and overfeeding, you should do OK ... good luck :smokin: