Feeding question in late bloom

Hi all...
I've been blindly following the GH Drain to Waste feed chart for my grow. I'm growing in 3 gallon with 1/4 SS#4 and 1/2 ProMix and 1/4 perlite.
Anyway, I've been feeding about once a week at about recommended PPM from chart...then water the rest of the week (usually 2-3 days later) then it's time to feed again by time it's drying.
I noticed some burning on leaves and yellowing over the last week or so. I thought it was probably a combo of the lack of nitrogen and liquid KoolBloom.
But today I decided to check and I watered in at 300ppm and my runoff was 1800ppm!!
Should I do a quick flush this late in flower (about 2-3 weeks left) or just drop feeding schedule for a week or so to try reduce soil PPM naturally by using straight water and letting it use some of the nutes in the soil?
Thanks

Edited to add:. Also...the pH going in with the water was 5.9 and the pH coming out was 5.75

Pics would be good, but...

Flush with straight water at 6.2-6.5, then feed with a normal feed right after the flush.

3rd Monkey said:

Pics would be good, but...

Flush with straight water at 6.2-6.5, then feed with a normal feed right after the flush.

Click to expand...

Thankd for the help....So do I want to flush until the runoff is pretty much the same as in the input water...or just bring it down to a reasonable level? I'll be flushing with RO water about 10ppm

tst2015 said:

Thankd for the help....So do I want to flush until the runoff is pretty much the same as in the input water...or just bring it down to a reasonable level? I'll be flushing with RO water about 10ppm

Click to expand...

2 or 3 times pot size is sufficient. Sounds like a salt buildup but without pics, hard to diagnose. Ppm isn't really going to help you in terms of flush runoff. When you run the nutes through right after flush, that's the one you want. It'll still be pretty high, but then you can water with more runoff every watering to flush the rest. Just make sure you give it a good dry after all that.