RDWC issues, how often to feed?

I have two plants going on a RDWC system using one main bin for water. Every week I do a full water change, complete drain of all water from buckets and bin. I keep my nutes around 800ppm. My plants are in flower and not doing great. Had issues during the entire grow, thought I had it fixed before going into flower and now it just keeps getting a little worse each day. When I test the water the ppm doesn't change that much, may drop a little. How often do you change out water and do you do additional feeding? I would add more nutes but the ppm is still high so not sure what to think. I am using Advanced Nutrients. Never had these issues doing a single plant.

Oldenred1 said:

800ppm

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that's probably your problem

Every nute SYSTEM is scaled up durring veg and flower, I should say most, not all

So keeping the feed at the same is an error

Pics of the plant

What nutes
Additives
Ph
Etc etc etc