first time growin, now problems begin during 4th week of flowering.

Ok this is my first season growing, haven't had any problems up till this pass week. I started to notice my leaves on the bottom branches were looking spotted and rusty. Now it has spread up from the middle now to the bottom branches. I have it in a large pot (well over 5 gallons) with MG potting soil. I was using botanicare pro bloom and botanicare sweet in small doses. its into the 4th week of flowering now and Im not sure how to fix this problem im having.
The Picture below is one of the leaves removed from the troubled plant. kinda out of focus but you can definatly see the rusted spots. The other pic is just the over all plant, that was taken about a week ago, and the pic of just the leaf was taken today (9-15)
ANY advice would be Much APPRICIATED.

You need to get a bigger pot and the growth should increase ten fold!!

yea a bigger pot wouldnt hurt but your plants gonna start doin that as it gets ready for harvest.. a majority of your leaves are gonna fall off and all that fun stuff....

it hasnt shown any signs of being root-bound. I wanted to keep it going till late October. I don't think thats the leaves dying off right yet. I wouldn't think so at least...

besides me needing a bigger pot what is wrong with the leaves??

did you check for bugs? spray the plant with some neem oil.

Spots on leaves: bacteria, fungal infection, insect sucking on the underside of leaf, if spots are orange in color it could be rust.

Doctor Optimara: Symptoms

Looks like spider mites, but could be several things mentioned. I had several in worst shape, and it was spider mites. I used the tobacco tea, then washed the plants off 20 minutes later. Then I got some maxi-gro liquid seaweed, and used that for spraying the plants. The tobacco tea works, but it scares me. The seaweed does great, plus it feeds the plant, also.

thanks, where would be a good place to get seaweed spray at?