hmm what comes to mind with me is, does the mg soil have fert already in it? if so it might be to strong for a seedling and is very lightly burning her or the ph is off which is very possible with mg soil most likely its to low. also you shouldnt have to water her at all for quite some time she hasn't even got roots to the bottom of the pot yet.
The yellowing and wilting is from the MG, it is burning the plants. Transplant as soon as possible into a very light soil something like fox farm seed mix. It is light and airy and will let the water flow through with no problem. Then when your plants have recovered about 10 days from then (remember feed them only distilled water) no neuts. You can think about adding some very, very very , week seedling neut. I like Grow Big, Big Bloom and Tiger Bloom, but remember a little goes a long way and a bottle will last forever. Also start out with only 1/4 of the recommended bottle dosage then work your way up from there, but only after you have completely flushed out the plants you have now. But get them out of that MG as soon as possible and pray the transplant wont kill them. Be very gentle with them when you do it and water them thoroughly the first time and put them back under the light. Then pray and it should work, how big are the plants now, can you send a better pic, I am no expert, I just went through the same problem and this is what the board said to do and it worked for me so listen to what everyoen else says and in the end you will have to make your own decisions, I can only tell you what worked for me. Good luck, bro...