In the pics it looked like it was only the lower leaves that were browning. Typically nute burn will show on most of the leaves all the way up the plant and it will start at the very points of the leaf tips and work inward with less initial yellowing. If the leaves are yellowing first across the leaves then browning, and it is occuring only on the lower leaves then that is typically something out of wack, like PH. Also you said that when you water, it runs through pretty fast, that tells me that they have used up the soil nutes and filled the containers with so much root mass that the soil can't hold the water and nutes to keep them from getting deficient.
If I am not seeing them correctly and they do have typical nute burn then it will take a while for them to recover. since you have cut out the nutes and are just giving them water for 2 weeks the overnuting should be corrected. If they are in enough soil (the FFOF is pretty hot) then you souldn't have to feed them pretty much throughout veg. If you have been feeding them from the beginning then it is a good chance that they are nute burning or the ph is getting way off. either way a good flush would ensure that any extra nutes is out of the containers and you can see what the ph is at the samne time.
I am honestly not sure which it is, but I would start with PH as that is most often a common problem. If you don't have one then you need to get an accurate ph tester, then ph neutral about 1/4-1/2 gal of water(adjust it to 7.0) then set the plant container in a bucket, of plastic tote or something that will allow the plant to sit in the water that you pour onto the plant. Then slowly add your water until it runs through and fills the container enough to come about a quarter to half way up the container. Try to find a container that is just a little bigger than the plant container so that the plant isn't swimming in a gallon of water. A quart is ok. Let it sit for about 1hr then test the ph of the water.
If the ph is outside of the range of 6.5-7.5 then that is a problem. may not be the problem but is a problem that has to be corrected. At that point you will want to flush the soil by pouring(slowly) 1-2gallons of straight water through the planters and let it drain to waste. Then get 1 quart of water or the normal amount that you water with and add a minimum amount of nutes to it and adjust the ph to 7.0 and slowly pour into the plant(s), let drain and then let dry out for a couple days.
If the plant IS root bound you can either transplant them to bigger planters with new soil added or you can just feed them with ph ballanced solution each time you water. I think all my info is correct here. I am not a soil guy so if any soil folks see something that I am incorrect about please correct me so we can get these girls back to healthy
