Root Temp?

So i have a hypothetical question. Say I had a garden with two seedlings and one all of a sudden just shrivieled up. Like it started to turn yellow at the baby leaves then the first set of real leaves just got brittle and broke off to the touch. But the grow tip and a second set of leaves were still in ok shape. Also the stem just shrunk so much, i though she was a gonner.

Solution: I leached the water thinking maybe when i mixed the soil i put too much blood meal. My soil is 3 parts hyponex(peat moss), 3 parts Perlite, 1/2 part MG, and 1/2 part blood meal. Its worked great in the past, for my past attempts. Any who i went to work and when i came home she still was the same. But not dead. Then i got to thinking i buried her deeper in the soil than the other one, so maybe I let the soil dry out to much, i did make them go another day to make the root strech. But I dont think it was this for i water them everyday due to the peat pots, and lots of perlite they dry out quick. Anyways I got to thinking TEMPS. The air temp is 75-80day and 65-70night thats fine. I noticed that when I picked up her pot it felt really cold. Root temp!!!!! I busted out my trusty digital thermometer and tested away. 58 degrees WTF thats to me seems like a problem I dont know. Any thought, comments or tips would be great.

couldnt tell you for sure but I always thought that roots preferred cold temps as long as its above freezing but could be wrong any one else?

ur right seeds endure the cold very well for that very reason... maybe its the blood worms i'd flush it out or summin, if u got an 11 or 9 leafer type of weed it will do better without ferts till its much older.

I do think it might be too much blood meal. Now it has effected both of the plants.. I took them out of there soil washed the rots with h202 water and transplanted them into new cups with 50/50 mix of Perlite and hyponex. I also turned off the HPS and put them under 2 cool 26watt CFL's. They dont seem any worse. The good thing is the grow tip still seems to be growing. Another thing is my PH is 7.0, not a huge deal but it could be part of the problem. Im gonna leave them under the CFL's until i see big difference. One of them i dont know if it will make it.