can anyone tell me what these spots on this yellow leaf are?

check this out, obviously this leaf is dying, but what in the world are those spots from. I had some fungus gnat larvae in the soil but not too bad. I azamaxed them out and sprayed with safer soap and this started happening the same day. This pic is like three days since that happened. I just watered and now its SO much worse. New growth doesn't look like this at all..

Hard to say and may not be anything to worry about. Don't know the size or age of your plant, but the location of this 3 point leaf at base of plant makes me not want to worry too much about it unless it is moving up the plant. This leaf is programmed to burn up early and every strain has a different way of burning up the leaves as they are exhausted. I have seen perfectly healthy plants use up leaves at bottom with these same spots appearing. Take a pic of whole plant if you don't think this is right. Good luck!

A lot of purple in that stem. Other leaves in the pic do not look good either. Might be nothing but need better pics and the other leaves and stems.

I have a cheese strain that does that to some extent. I was worried and searched it out. The photos you may find would suggest a calcium/magnesium deficiency, but don't go doing anything just yet. What Bugeye says holds true. I gave a clone of the same strain to my buddy who grows completely differently and he has the same issues on the oldest fan leaves. The cheese is the only one of 4 strains that do it in my garden and they are all treated exactly the same.

More pictures of the entire plant would be helpful though, as suggested by Da Mann.

you're not letting it dry out.....................

hence the gnats.........hence the P lock.........................don't do that