Can anyone help me?

OK I have two plants strain unknown under a 250 hps light they are looking pretty good they were both very very green now my one plant its short and bushy and the other tall and thin. the tall and thin one is starting to yellow a little and a few of there leaves on the bottom are pretty much dead should I cut them off the plant also its in a very small pot and they are over a foot tall is this a problem should I transplant and will it live. I have them both in mg potting soil for almost two months now should I start giving them nutes. what can I do any info will help thank you.

Most likely time to transplant, look under pot at bottom and see if there are roots coming out of bottom of pot, if they are I would say transplant. they should get nutes, by now, but if you transplant remember the new soil,Mg, has nutes in it already so wait at least a couple of weeks after transplant to feed nutes. You could cut off leaves that are over 50% dead but i just pull and usually if they are dead they will pop off very easy.

are u feeding them? are they in veg or flowering? for that small light 2-3 gal pots will be fine, and yes FEED them.

Yes, transplant asap. That'll take care of any deficiencies, plus, give the roots the room they need. Also, if you must use MG soil, buy some perlite to add to it. Most places that carry the soil, also carry MG perlite for like $5 a bag. Add one bag to each bag of soil,(two, is even better, but one will work fine) and you'll be much better off, than having no perlite at all(helps prevent overwatering, for one). I think you'll be surprised at how much better they look, a week or so, after the transplant. Best of luck to ya.

Sounds like they are hungry. Give them a light feeding and see if symptoms improve. If there is severe wilting a few days after feeding then that could be possible root bound but it sounds like they just need nutrients. You should start feeding them as soon as they go into veg and if they are even close to a foot tall and you haven't fed them yet then that is for sure your problem.