Yes it is a lack of nutrients and by the clear colour I can tell it's an old deficiency , you can't fix the yellowing but you can stop it with a feeding and as it's almost the end of your grow I would recommend you to go with the high dosage to be sure that she'll get everything she needs to achieve flowering and bud fattening .
If you don't feed my guess is that the lack of nuts wll makes the leaves get yellow and fall so you'll have to consider an earlier harvest widow than expected