Is it possible that maybe I underfed my plant and ...

This is what I see based on the photo's . Firstly , you're plants are suffering from a couple different things here the first real problem I see of course is the yellowing . This is being cause by a combination of 3 things , firstly your plant is suffering from nitrogen deficiency , this is the broad yellowing that's taking over your lead , it's also suffering from CalMg problems this is the yellowing that you see that has started in the middle of the vein's of the plants leaves and lastly PK deficiency more Potassium tho , I can say this because i can see the spots starting on your leaves and they are just random spots they will turn brown eventually and get bigger . This problem is a real easy fix all you need to do is adjust your nutrient solution and these ladies will regain there health and be rocking and rolling harder then before . I would advise that you do the full dosages of PK which should be 4ml/l with fully mature plants and I would bosst the grow part ever so slightly by 1ml/l as well as add 2ml of CalMg per litre of nutrient solution you mix up . This will do a variety of things for you but most importantly slow the yellow restore the not so damaged leaves back to normal and continue to grow prosperously . For the leaves that are too damaged and will not heal properly I would advise that you remove them so they dont make a perfect nesting ground for unwanted intruders such as mites , scale , miners .. the list continues its just over all beneficial to remove those leaves :) Over all your doing well just a few things to touch up and this will be epic ! I hope this information helps you to understand whats happening a bit better to your plant and the very very easy ways you can fix it. -Happy Growing!