Can someone help identify whats wrong with my leaves?

Hey,
Background to the plant is she is 3 weeks into bloom, in a soil mix, 3 gallon pot, she not over watered and for last week she aint been misted with spray bottle.
I have just pruned these leaves off her plant (only because they have more than 50% damage)

Is this a def. like K or is it cause there was small amount of standing water on them one day last week and its leaf spot or rot or somthing along those lines.
These are some of the lower leaves and there no damage on the tips of branches and up top looking good. Nice ..
As you can see theres the yellowing and browing from the tips and dark spots forming. Curling of the leaf is either up or down, some no curling.
Sorry if pic quality is abit bad.
Thanks for any advice or help with this, and have a good day..

how long have they been in th 3 gal pots, wut kind of soil is it, r u using nutrients?

Hey,
Id say she was in pot from she was transplanted at week 2, so very young. The soil, and I ready for some flack, is MG potting soil. as it was cheap and I didnt have the cash to get perlite or somthing else to mix with it. As for ferts she was on a NPK fert of 24-8-12, also MG. and next weak I am going to go get a fert for the bloom. Once again cash is tight.
The soil pH at the moe is about 6.5, thats from liptmus paper so quite rough guide.
Hope that helps , need any other info?
Could it be she is abit big for the pot?? Could it be she is pot bound at the moement?
Take it easy....