Sudden yellowing of leaves (first time grower)

Hey Growmie ... This can be caused by too much nutrients, lack of nutrients, or even from the lower leaves no getting adequate light. Hopefully, this was helpful and remember ..."Happy Growing" and "Free your mind one puff at a time". Mr_Weeds_Autos.

They need nutes bad

Wow, should have looked at more pics.. Looks liek N def and a 2nd issue -- maybe magnesium deficiency because it has a interveinal chlorosis accompanying the spots, but possibly Ca. I thin you have 2 different things going on.. I think it is deficient in N, though. I think pH or imbalance of P/K/Mg/Ca exists... but could be ca/mg def coinciding too. you'll need to consider what you feed to eliminate possiblities. pH, concentration and ratio of nutes are all equally important to availability.. oyu can easily have an abundance of something and the plant still doesn't have access to it, if the other 2 factors are off. that's why anyone who tells you something confidently about this, even if they end up being right, is just smoking too much. So, check teh easy stuff first -- pH, calculate ppms of what you've feed etc etc.. then deduce further, then think about adding something or taking something away.

there is a bit of Nitrogen deficit (yellow leaves starting from bottom up) the spots are most likely from salt buildup on the roots. I presume you are not working with a pH tester? what nutrients do you use or have you started giving any? When watering, give as much as you will get 5-10% off in the bottom tray. In this way you will prevent salt buildup. Make a 5 L water solution with some good nutrients and give it. She'll be grand!

Just yellowing can be underfed or overfed and lockout is happening. I would plant to something a little larger and run ph water through and start your nutes over if you dont know why.