23 day old seedlings + deficiencys?

I have checked both my book and online for this problem and am pretty sure I think its magnesium and calcium deficiency but for a first grow I am going to throw a life line out there to you guys. There is one seedling that looks good. I tried feeding them a week or so ago with i think it was foxfarm grow big, half strength one time - because there was one smaller seedling that looked like it was week and falling over (still sort of is) and around the next day the plants already started showing signs of discoloration and i'm just looking to know whether or not its nute burn or a deficiency, and how to fix this. the strain is unknown, it was from some poor bud that had a ton of seeds..but my main concern is the growth size. I've looked up a few other "23" day old or at least in that area plants and they all seem like they have grown a lot more than these, Just something that i'm hoping someone who has been through it a few times could take a gander at. i've started with regular non ro water for seedling growth and now i'm back to using it because i don't want to do more harm but still want to give it something to eat at least. watering maybe once a day. ps the second picture is that random seedling that dipped over and seemed weak and now it peaks up here and there.

thank you

im no pro at this but you do have a problem im growing for the first time but i have alot of help from people who know what to do. my plants are 3 weeks tomorrow and twice the size if not bigger i think you need to start with the water/ nutes a half dose first time may be to much i was told to start at a quater dose. do you check your ph lvl and ppms a bad ph could keep the plants from growing i always and my nutes and then check ph. If you have a good ph and a good ppm then you might have a def problem but if you ph or ppms are off then it could cause your def problem

Great info actually. Well, i checked the ph for the nutes not for the water because when i originally didnt have my ph meter calibrated and never thought the ph was bothering them since they were growing but i'm guessing that is what stunted the growth since you say yours are 3 weeks and twice the size. dang dude, back to square one. I'm not sure i caught what you said right, after you sowed your seeds did you immediately use 1/4 dose nutes for watering or did you wait a week or so before feeding nutes?
I'm gonna have to germinate some more seeds tonight and throw them in there too with a better starting point I suppose..LAME.

i grow with soil organic so with nothing added at 1 week i start with a quarter and increase by the week only watering once a week but with thats said my friend uses hydro his first shot at it a few years back he had slow growth and small amounts of bud his cure was buying bottled water and getting himself nutes made for growing from your local hydro store found all problems were from bad ph from tap water

mine three weeks

ITS NUTE BURN. Just switch to distilled or tap water with no nutes and it might go back to normal but you have nothing to worry about.

awesome. i'm going to germinate some seeds tonight in ph'd water after i install my RO filter. and run them under the other set of lights, and keep those going to compare and contrast. maybe i'll switch these to 18/6 in the mother room give them some sleep. I have better nutes coming in this week, ill use 1/4 dose on those when these heal up
thank you both

You have some nute burn, but it is pretty normal that young with hydro, and will probably grow out of it. DO NOT FREAK OUT. Seriously. I have little clones that are all burnt up, and gnarly looking too, but it is fine. I bet in a week you will have an explosion of growth. Your plants are just now starting to veg instead of spreading it's roots.

They unfortunately seem to be all dying off though two still kind of look the same, but will probably not survive either and i bet i will get slammed with all males. lame. back to the drawing bored dudes. on the like 3 still sort of hanging on to dear life it seems the new leafs are growing in in a weird manner too like binding up or something. i've got new seeds germinating now blah. i wonder if the temp makes it worse too, its around 58 degrees in there.