Absolutely nothing to worry about. You've said it yourself, its older growth thats affected and yellowing which is normal as your plant uses up its food in its stores (leaves). The light isn't reaching the bottom growth of your plant therefore photosynthesis for the older growth is no longer occurring. The only time you would worry about leaf yellowing is if it was the new growth, then this would indicate a problem. I see you're still giving it veg nutes which is correct for the first 3 weeks of flower which is the only time you will need to be giving it the doses of nitrogen to support the plants vertical growth, after that you can gradually cut it out completely as it can hinder and slow down your plants bud growth, don't get me wrong you can still use it but it wont give you optimal bud growth which is what you want for flowering. So no, you don't have a deficiency in my opinion. Give your girls a bit of LST to open her up and get as much light through as possible as its critical if you want to see a nice yield come harvest day.
I would also drop your humidity unless you want mold forming on your buds, 65% RH is way too high for flower. You want it in the range of 30-40% to minimise risk of mould and to see some nice trichome production. Do a bit of your own research also if you're not sure, information is easy to find. But yeah optimal RH for flower is 30-40% and even less in some cases in the last few weeks of flower. Good luck.
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