EC/TDS/PPM and pH Acting Funky

For example:
Fresh 30 gallon reservoir full of RO water with 1mL/gal Zone, 2mL/gal CaliMagic, 0.5tsp/gal MaxiBloom, 2.5mL/gal liquid KoolBloom.

Day 1 - 840ppm - 5.6pH
Day 2 - 800ppm - 5.9pH
Day 3 - 800ppm - 5.9pH
Day 4 - 820ppm - 6.0pH
Day 5 - 840ppm - 5.6pH ( adjusted from 6.0pH using Mad Farmer pH down)
Day 6 - 880ppm - 5.9pH
Day 7 - 890ppm - 5.9pH

This is happening to all 3 of my flower rooms and both of my veg rooms. Plants look very lush and healthy in veg but they decline rapidly once put in flower. Thing is I still yield 5-10 oz per plant with a 6week veg. I use 2.5 gallon ebb&flow buckets from rooted clone to harvest.

Another thing I've noticed, NO STRETCH! I have run the following strains and none stretched. They get bushier but gain no height. I've measured lol.

Strain ran in my setup with no stretch:
808 Headband
Deep Sleep (Larry OG x Pre-98 Bubba)
Chemdawg D
White Widow x Big Bud
Chronic Thunder
Northern Lights #5 x Big Bud
Blue Dream
Querkle