New Grower Calmg ? Issues need help

[CaptainKush88]

So im having problems with 3 plants im growing.. i do have a grow journal going.. im only growing the three right now they are about 4 weeks old day 31/29, growing in root farm coco mix with root farm nutrients and remo cal mag. Startrd feed the girls at about 2 weeks old and started addin cal mag around week 3.. girls get 18 hrs light from my cheap amazon full spectrum white led.. temps are a bit high ranging from 28-32 °C With light on to about 18 when off.. the love potion has been shooting pistols since day 15 and the lemon skunk and northern lights big bud since day 25.. I've been giving the girls nutrients every feeding since I started the notes.. recently let my medium dry out because I'm having issues with gnat flies and since I fed them 2 days ago they've been stretching like crazy but the other day I noticed some light spots between the viens on a couple leaves on the lemon skunk which then progressed and turned to an orangey color and now has spread to s few more leaves and now I'm having a similar issue starting on the love potion but the light spots that started on the lemon skunk are more towards the edges of the love potion... also on the nlxbb some of the older leaves have some orangey/goldish spots between the viens that is slowly taking over most of the leaf.. first pic is the garden last night, second pic is a two leaves from the lemon skunk showing the early signs of the issue 3rd n 4th pic show the progression on the same leaf. 5th nd 6th pic is the the leafs on the love potion and the last pic is the issue on the nlxbb... any help or suggestions would be greatly appreciated

 

[CaptainKush88]

Also forgot to mention alot of the stems on all three have changed to a red/purplish color since the last feeding as well

 

[Jackson]

Are you checking ph?

 

[CaptainKush88]

Are you checking ph?

Yea I have been checking the pH of my solution going in but have not been watering to runoff every time.. i gave the girls 4 liters yesterday and none of them had run off so i mixed another 4 ltrs and watered them all till I had some significant runoff.. I checked the ph of the runoff and it was at about 5.2 so I feel like even though I'm giving the girls a full dose of cal mag they weren't actually getting the nutrients because the low pH.. did a small trim after I watered yesterday and they seem to be doing great.. no further leaf deterioration that I can see so hopefully that's all it was was a cal mag or other deficiency caused by the low ph of the medium..

 

[GeorgeCloney]

Yeah 5.2 is a little low.
Also , the purple is a first sign of magnesium def'c..you can give the plants a 50 to 70 ppm addition of epsom salt to fix that. But not more or else you're gonna start a new condition where the mg is gonna lockout the nutes.
I strongly recommend that you do this with an EC pen.

 

[Waira]

pH is too low mate, get that up near 6.0,... you have a lockout, likely of both P and Ca,....