The first thing I would recommend would be to take a soil sample, make a slurry with it, and test the pH. If the pH is higher then 6.5 then I would recommend pHing your water and feeding solutions closer to 6.5 from here on. If you are feeding at full dose then you may also be running into salt buildup in your pots. Both pH issues, and salt buildup, will cause the plants to have issues absorbing nutrients so those are the first to things I would look into. If you are worried about salt build up then look for a chelation solution to mix into water to flush the pots to pull that extra salt out. One of the ones I've used is called "Flawless Finish" from advanced nutrients. I'm sure a chelation solution could be probably made at home for much cheaper, but I haven't looked into DIY recipes for one.