my bottom leaves are frail and dark

i have a 75 watt florescent light about to get a mh. my plant is a little over a month old and is only a foot tall. i got potting mix from my local nursery and am using miracle grow house plant food with 8% total nitrogen and 7% available phosphate. i just flushed it today in the bathtub with tap water but ive been using purified water. the bottom leaves have wilted away and i cut them off. now the next bottom leaves are frail, darkening, drooping and curling under. the leaves above them are kinda curling up. i have a small closet with a fan and a heat lamp ive been using once in a while. please help me b4 i lose my first plant. here is two pics.ty

How often are you feeding them? Do you know what the PH of the water you are using? Did the soil already have nutrients in it? What are the temps at? How often are you watering it?

i feed it every other watering so every 4-5 days.i havent found any ph strips yet can you use the ones that test the soil. my soil is family tree nursery professional potting mix,family tree is the name of the nursery and it doesnt say anything about nutrients. its ingrediants are blend of canadian sphagnum peat moss,composted pine bark,horticulture grade perlite,dolomite lime and a wetting agent. i dont have a themometer in there but id say its 78 - 85 deg.