Mg Def? please help!

[kiefisgood]

White Widow
1 plant
Vegative stage week 3
Indoor Secret Jardin 120 4x4x7
Hydro 5 Gal DWC
Res temp 69 F
rockwool/hydroton
It is under 1 400watt MH air cooled
Room Temp is 70-75
Humidity is low 15% - 30%
EC - 1.7
PPM @ .7 - 1220
PH - 5.5-6.0
Using GH Lucas Formula no other additives
LST and TOPPING

Ok here is the problem. I have these brown/rust/whiteish spots forming on the older an leaves. They seem to start at the tips and work their way towards the base staying for the most part in between the veins. I have heard of people getting Mg defeceincy using Lucas. Any ideas guys and gals? BTW this is my first thread I do hope I did it correctly.

 

[kiefisgood]

Here are two more pics

 

[PrairiePoet]

Is your water RO or tap? Looks like a CalMag problem to me. Might try adding 1/4 tblsppon of Epson salt per gallon and see if that helps.

 

[kiefisgood]

I'm using ro water. I bought some botincare cal/mag. Any suggestions on feeding with that. Should I flush everything first?

 

[GrowCannabis2]

Use the cal mg as recommended since there deprived see how it does yellow ubdead spots should turn green again in a couple days u still may get die off if the problem still continues at full strength then start boosting it by a ml or two at each feeding. I had to boost mine an extra 5 ml over recommended with advanced calmg bloom when my girl got mg def but it helped a lot and now she is the most sugary of the bumch but the stress did cause her to hermie