New to RO: seeing deficiency quickly develop 3 wks into FLR. Mag or Nitrogen??? Pics

Few grow details:
Ebb and Flow of 5gal buckets with Hydroton clay
Ph around 5.8 - stays pretty steady
PPM 750-800 @ 700 conversion - Also stays pretty steady
Flooded 2x/day, 12hrs apart
RO water
GH 3 part with calmag+epsoms, PK boost for FLR - Ratios listed below
Temps 67-79, humidity normal


I have been a successful grower in the past with my personally tweaked schedule of GH 3-part with some epsoms and additional PK boosts during flower.
However, water at my current location went hard in the middle of the summer and I purchased an RO filter. Everything was great at first, I added Cal-Mag at 5ml/15-10-5 of 3 part and set my concentration at about 750 ppm on 700 conversion factor.
The actual numbers for 100gal of solution were:
450ml gro
300ml micro
150ml bloom
150ml calmag
and 4.5 tsp epsom salt

They seemed quite happy with this through veg, but in the second week of flower(after switching to the inverted FLR formula) they started to show some yellowing at the bottom. I interpreted it as magnesium deficiency and upped the calmag and epsom for the third week considerably.
Numbers for 100 gal:
125ml gro
250ml micro
375ml bloom
300ml calmag
6 tsp epsom
250ml P/K-13/14.
Still around 750 ppm @700 conversion and kept at 5.8 Ph

But the deficiency only seemed to accelerate, some light brown necrosis can be seen in the 4th and 5th pictures. I am not sure if it is magnesium deficiency or possibly nitrogen deficiency(can't tell if its interveinal chlorosis), which the visual signs suggest. But by adding extra calmag plus, I have already added more of both!

I have also added a high dose of PK booster, however I have always had great success at that rate in the past...

Thoughts:

Mag
I think it looks most like magnesium deficiency, but I am adding so much calmag and epsoms that I dont know if thats possible. Mag could be getting locked out by too much calcium, but calmag supplies both in proper ratios, plus i am adding extra mag to the cal/mag ratio with epsoms. Mag could be getting locked out by too much potassium but I have used similar levels without any problem in the past.

Nitrogen
It also looks kind of like nitrogen deficiency to me, but I am not sure why I would be seeing that at this point.

P+K
I really dont think it is Phosphorus or Potassium deficiency, I have dealt with both aplenty and it resembles neither.

Ph control
I keep very close watch and maintain Ph in between 5.7 and 5.9, usually at 5.8. This has always worked tremendously for me and I dont believe Ph is causing this problem..

UNDERWATERING
I am new to Ebb and Flow schedules, used to be a DWC, and I am ONLY FLOODING TWICE/DAY, 12 hours apart, even though the plants are 3-5 ft and bushy. They do have quite a bit of clay media to fill out with roots and I never really see drooping from thirst so I kept it infrequent to avoid rot.
Is it possible that the plants aren't getting enough nutrients simply because they aren't being flooded enough?

ANY INSIGHT IS GREATLY APPRECIATED!!! I have tried to include all pertinent details, but please dont hesitate to ask if not...

Your N is low then leafs go yellow its normal.
What kind of water do u use? Distilled water if its more different
if not u can pu your ppm up to 1000 in this photo

Does anybody have any thoughts on this matter?

After further analysis, I am still under the impression that I am seeing magnesium deficiency And i'm thinking it might be as simple as I'm not adding enough cal-mag and epsoms to compensate for the RO water.

How much Cal-Mag do growers really add?
In my experience, label instructions should be applied at around 50% or less. And I was using about 60% of the recommended 5ml/gal. This even seemed high to me because I am at about 25% of the recommended concentration of the 3-part base nutrient. example: recommended @ 5/10/15-->500/1000/1500 in 100gal. My normal in 100gal: 125/250/375
Also, the 60% of recommended cal-mag plus 6 tsp of epsom salt brought my concentration from 5 to ~260ppm which seemed more than enough to me.

Therefore I have been weary to add more than 60% of recommendation on the cal-mag. However after more research it seems that some people really do add the full 5ml/gal of cal-mag to start their nutrient formula. The thing that shocks me is this comes to about 375ppm before adding any base nutrient. Before I switched to RO water, my starting ppm was around 100 and I was able to keep my total concentration as low as 700-750ppm throughout the grow with very happy plants. But it doesn't seem very feasible for me to keep the concentration that low if half of it is Cal-mag!

How much Cal-mag do you guys actually use with RO water?

And what sort of total concentrations do you guys end up at including base and additives?

Is there anybody who uses RO/Cal-mag and also likes to keep concentration low? . . . Opinions, examples, advice?

There should be enough mag/cal in your GH nutes unless ur not using it at full blast. I run my GH at 1200ppm and I only have to supplement with cal mag once during flOwering

Please I need some input on this issue, I know people out there are running systems similar to mine...

a few thoughts on r/o's ( basically the user's manual directions ), the carbon part should be replaced on regular basis , if carbon stops absorbing chlorium and chloramine it wrecks the core of the r/o unit

IMHO, based on pictures only; Nitrogen-def.

Dang bro your not feeding them thats it 2x a day is horrible for just hydroton do you have rockwool in there? If you got rooter plugs or something similar in there that holds the stem up you need to feed them girls every 15min on 15 min off hurry bfore you kill them ladies feed them NOW! THATS IT! Not to much nutes no cal-mag get some hydrogen perxiode 3% and use that in the resv and thats it you read to much into it. HURRY!

i'm agreeing with the post above. twice a day for such massive bushes (nice going!) sounds like too little for hydroton. you should water every time the medium becomes dry (or a short while after that). oxygenate your water well and keep temps below 75, then you won't have root rot and overwatering. This is hydro man.

I have used RO water (with HESI nutes) with only epsom salt no calmag - in coco, and had no trouble.