Sorry to jump on a thread here iv had my clones potted up for maybe 4 days now would you say judging of the pic maybe mag deficiency?
Not low Mg but possibly P. Have the tips you've snipped off looked like the damaged ones not yet snipped? That is a good practise for when you try to correct a problem. Remove all the damaged parts so you can see if it keeps happening still and maybe change tactics.
You should really open a thread in the proper forum like Marijuana Plant Problems where more eyes will see it. If you click on Report and ask really nicely a hard working mod/admin could move it over there with any replies you should get before the move.
More info like soil, nutes if any so far, temp, humidity and what kind of water used and it's quality or lack of is very helpful to any of us that stick an oar in the water to try and help.
With low P the tips will burn like yours but I'm not seeing blueish green in the leaves or the purplish petioles. the damaged bits I can see are a lighter colour than described here too.
Low Mg is like this and readily noticeable in the older leaves. Looks striped at first then develops spots on affected leaves as it gets worse. Easy fix with calmag or epsom salts from the drug store.
Here's the whole chart so you can play detective too. Save it if you can for future reference. And you can download lots of good pot e-books in 3 formats at
PDFdrive.com. Just search for pot, cannabis, marijuana etc to find loads.
Don't forget to ask for the move.
