Fucked since birth. rusty spots on fan leaves.

I started 6 seeds almost 3 months ago. I started them under my skylight and then started moving them out doors. This one was the runt of the group. He was fucked since he sprouted but since it wasn't costing me anything to keep it growing i just left it be. It looked like it was going to grow out of it but the little rusty spots are now catching up to the upper fan leaves. Its just started flowering and would like to keep it as healthy as possible. Here are some pics. Tell me what you think and how to fix the problem.

Thanks

Im not sure what it is. I would guess that it is coming from your soil because I believe that the water / nuits flow up the stalk, up the center of the leaf and then to the fan part of the leaves. If you look you have all the middle of the leaves burnt/damaged. I would suggest a complete flush of the soil. What is the PH of the water you are giving them? What supplements are you adding and how often?

What you have is a calcium deficiency, this can occur for various reasons, i can see your girl is lovely and green, so it's not a shortage of nutes as such but i'm thinking perhaps your running the wrong ph so the plant isn't getting the nutes it needs.
What ph are you running this girl at ?

This was my 1st grow so I did a lot of weird shit.... I started off just wanting to go as simple as possible. Just add water approach but as my grow went along i started reading about which soils are good and nutes and other shit..
Anyways all 6 plants started off in MG soil in the little 3x2 starter trays. Then got transplanted into 1 gallon pots with MG. After this i got some FFOF and transplanted all but one of my plants into the FFOF. The plant pictured above is in FFOF. Since it was the runt of the group i just gave it PHed water. It has had those spots on all the fan leaves off the main stem.

My water ph is somewhere in the mid 6s.

mid 6's is too low, you need to be nearer 6.8 this is what i call the sweet point...
With regard to those leaves that have discolored, they will NOT get any better, flush the soil and add a higher ph and hopefully she'll make it full term.