First indoor grow, 3rd week flowering problems, very important need help

Hello all,

First let me humbly say I have been reading on here for very long and have been cautious to post anything yet as I wanted to just do this for fun.

I am growing seeds from an unknown strain. The bud was dank and had mad crystals but it also had 3 seeds in a very large amount of nug.

I saved these seeds and have been growing them in a very low cost setup (I have a big cardboard box lined with tin foil, used a 6500k daylight fluorescent and when flowering started added a 23 watt soft white light with the regular daylight fluorescent.

The specs:

Veg'd for 4 weeks with 20/4 lighting, induced flowering with 12/12 about 3 weeks ago and the plant has been looking great. We had two but one was a male and we just killed it.

Anyway we have had great small plants that were always healthy. When flowering started I introduced (at very small amounts first) a houseplant special water soluble plant foot which is 15-30-15

PROBLEM PART

All has been well with the plant until 2 days ago when I noticed the leaves on the lower nodes were curling up. Now it seems they have started turning brown in some spots and are turning yellowish at the tips and obviously dying off.

I am very scared my beautiful plant is going to die and any help assessing this problem would be more than just appreciated.

Please let me know what you think, I have done a lot of research and cannot pinpoint it.

The pictures are from earlier stages to where it is at now.

Also the soil is just regular soil from outside my house, it is decent soil though, not hard clay. I have not tested the PH of the soil but will do that soon as well.

wouldnt worry to much yet mate, quite a few plants start to lose bottom leaves in flowering, just pull them of to stop wasting any energy on them, if it gets worse then could be nute problem, over watering or a heat issue...