ph issues or nute (Mg) deficiency?

Looks like its just hungry. Or dying probably getting ready to die. You could try feeding it but remember slow and low with any nutes especially in soil. Honestly though its probably dying and ready to fade and get chopped down

You're still at least 4 weeks away, you shouldn't have yellowing like this yet.

You're ok IMO. At week 10 of an auto you aren't need much if any nitrogen. Assuming your variety is similar to other Chem autos you shouldn't have much longer to finish and yellowing is pretty common the last couple weeks. Your soil might be a bit depleted at this point but I wouldn't add anything beyond a tblsp of molasses this late in the game on an organic grow.

Your pH should be a little higher but such a small amount shouldn't affect the nute uptake that much, which is why PK excess is still my first guess. Unless you have no nitrogen at all...

N issues would be unlikely at this point, so my guess is that you are using too much of a bloom nute that's locking out micros like magnesium. PK excess locks out micros.