3 out of 5 plants serious drooping on gt604

I woke up this morning, 2 plants at the back looked over or under watered, checked res, its tank change day so I changed the tanks.

I'm on the 2nd week of 12/12 today, change from aqua Vega to Flores & went full strength big bud & stopped root excellerator.

Ec at 1.0
PH at 5.5

I notice a hour after this, the 3 of the plants closest to the declined slope leading 2 the red started looking worse, I've been trying all day to rectify it before lights off, I done the best I could.

Symptoms: stems losing strength(to the point of snapping)
Leaves pointing down(still healthy green)
No clawing

Its as if all the stems are losing their strength and just flopping as low as they can go

I have 2 airstones in each of the gt604's, its only 1 of the tanks that's getting the issue, I thought I'd done the res temps too hot so depleted oxy, & plants were being overwatered. No purple stems.

I've tried adjusting the flow, air 2 the oxypump and mimicking the other gt604 but it didn't look as if it was helping.

Last but not least, I added a bit wood to adjust the flow-rate angle. (Hopefully see a difference tomorrow!

Sorry I couldn't post pics as lights off, any ideas?

Anyone???

What is your solution temperature. How do the roots look/smell/feel?

Root temps cooled down before the lights wenT off..

It doesnt smell as clean as the other tank thoigh even though both tanks were changed, ive been using cannazym since the start

Roots looked white though