it doesn't look like nutrient burn to me....
It looks like to me that ur plants are entering their last push to flower and are now in the final stages of their lifecycle. So what you get isuniform yellowing beginning at the bottom of the plants and working it's way up.
When this begins to happen there isnt' much u can do to stop it. Depending on how far along they are , and they look like they are a ways in and about a couple weeks from harvest. Everything is fine and they are nearing the end. EDIT: this info is only relevant if you are within 2 -3 weeks of recommended harvest time!
I would begin to water with plain water only until they are ready to harvest.
Looking at one of the pictures you gave us, it also looks like you could be experiencing lockout due to salt buildup, which is also possible. After some serious staring at your pictures Mg def could be your culprit, which in later flower is usually caused by salt buildup in the soil. A good flushing of the soil should bring the salt levels down to manageable and the plant should be able to tolerate it.
The upwards cupping of the top leaves tells the tale. feedings every 4-5 days is overdoing it, even with a semi organic fert like fox farms.
However due to lowryders short flowering period i have a feeeling that a "few weeks" is having u getting close to harvest time. 2 more weeks of straight water and i would pull em. Overall the plants look like they are just nearing the end man.
feed em plain water from here on out and you should be happy with the harvest.Lowryder isn't normally a huge producer. There are some out there that find special pheno's from the lr#2 and LR but they are few and far in between and are not normally huge producers.
