Leaves are getting light brown spots and turning VERY soft?

I have some very young seedlings that have their first 2 actual leaves and 2 more very small ones comming out the middle, but a couple of the plants are getting brown spots on the leaves and all the plants are starting to get VERY soft curled leaves. Do you know what could be causing this?

at the time i dont have a very good setup but tell me where my biggest problem is.... i have one of the really really big laundry baskets with a lid and a 2ft flouresnt buld and 2 regular light bulds for heat becauase its winter time here (gets to around 20 degrees) and this is in my barn. underneath one of the lights i have a tub from a tub of butter full of water so it will evaporate into the air. i have all my small seedling in water bottles that have been cut in half (9 seedlings) and i have one plant in a tub from a tub of butter thats quite older but has had a very very hard life from being over ferilized because this is my first grow and on the side of the laundry basket i cut about a 6x6" square out of it so it has a little circulation.


My guesses for the wilted soft leaves is either over watering or stress from cold temps. But about the over watering. I water my plants and then a week later the dirt hasnt dried out much at all so im guessing thats caused by cold temp. . Tell me what you think?

I think your temps are so cold that the plants are not transpiring fast enough to use much water, and it's even possible they may have been exposed to freezing temps.
Before you are going to have any success, you are going to need to get control over yout temperature and ventilation.

well when it started doing this i only had one of those light that are used to hook onto the hood of cars so you can see i was only using that for my heat now i have a desk lamp in there but it get around 20 degrees here at night time and the only time of the day i can check on my plant is around 3pm-4pm which its usually around 40-50 at that time and i put my hand inside the box and it feels extremely hot so do you think it could really be getting that cold at night time (this is after i put 2 bulbs in there for heat)-----------also is there anyway to keep my plant from getting really tall and just keeping it fat and short i had an idea of tieing it down sideways and seeing what that does but i thought id look into it first