2-3 old Weeks Jamaican weed

2-3 weeks old ..only about 10-13inches tall. The lowest leaves have dryd up and curled, the next top 2 have spotting of dark grey and light brown spots ontop of the leaves. The 2 top(newest leaves) are fine and green.

I have used to much water(few days ago) and have started to let it dry out.

Any suggestions on whats happening?

So this is a Soil grow? Lighting, water? PH? Details please.

soil : shultz potting soil plus
lighting: 50watt incandescent flood light
ph level - neutral

sorry no pictures yet but not worth taking because its my first trail plant.
Its inside a 12pack beer case, with tin foil around the sides.

I recently just got new soil(shultz potting soil plus) with plant plod - plant fertilizer and moved into 12pack beer case.

An empty beer case, coated in foil, with a incandescent light bulb in it sounds a lot like an EasyBake oven. You might well be cooking it. Even if it's not too hot in there, you would be better off with a Y-splitter with a couple of compact fluorescent bulbs instead of an incandescent bulb. They produce more lumens, in the proper spectrum, cooler and more efficiently than a incandescent which may or may not be the right spectrum, but is definitely not intense enough. A multi-pack should be pretty cheap, just try to find some that say 6500K somewhere on the box.

With just an incandescent bulb, the most you'll be able to grow is a long stem, maybe with a few sporadic "mole" hairs if you're lucky. They just don't cut it for indoor horticulture because of their weakness and how many of them you would have to have.