Im using a mix of of FoxFarm Ocean Forest and Happy Frog with added Bat Guano and worm casting. With every grow I get the " red dots" on my leaves. Then Im adding Cal-Mag every watering.
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High powered LEDs 
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Im using a Mars Hydro TS1000, 150 watt in 2x2 tent. Biggest I can fit in the tent.
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Plus 2 each Deep red and the UV leds
Led lights???
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Use the search function up there 
Type in “cal mag issues with led lights”
There is a lot of info
Just a thought
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Using FF? My experience also with FF and LED. Also the type of water you use can play a role. RO or distilled are free of any cal or mag.
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I was using my well water. But the PH is so high. Now Im using RO/ distilled- refilling at supermarket water that comes in at neutral for PH. Im going to keep double dosing Cal mag and see if I can stop the red dots from getting worse.
Im always learning how to fine tune my grow. I had no idea that the fans blowing directly on the plants/ buds is also bad. I figured I was keeping mold away and strengthen the stems, instead I was drying out everything.
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What’s your well water source TDS? You could mix the well and RO water to save on the trips and $. As @Docnraq mentioned the calcium deficiency is related to your RO or distilled source and not having any calcium. Magnesium is another critical secondary nutrient not found in these 2 water sources. . .8-1.2 grams of Epsom salt will provide the magnesium and sulfur. Post a pic of your concern and what PPFD are you running the light, higher lighting intensity can demand an increase in calcium 
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Use some epsom top dressed i suggest. Ro has diddly and needs it. My reservoir has plenty calcium. Mag light. Here is a current issue. Mag light. Calcium prob followed. Added epsom and recovering nicely. Notice the spots appearing after mag deficiency.
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Do you have a picture of what you are experiencing.
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Dont try a ph meter in distilled water, you wont get a read and will ruin meter.
Respectfully disagree Growmie, distilled or RO should have a neutral PH of 7 and I rinse and clean my Apaera 20 with distilled before I store in the storage solution. I think you’re confusing TDS with PH
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I dunno where you got that but its not true.
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This says storage not taking readings
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For storage use
I use a ph meter 5 days a week for a living. I assure you, distilled water does NOT ruin a ph meter. If it did, Id be going through meters like candy.
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I cant argue with that I’m going by stuff i read and when i did ph distilled once with my milwaukee ph 55 pro it started reacting very slowly after that but if you do it all the time I’ll trust your right
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Im on well water too. Been using 1tsp/gallon of vinegar to get ph down from 7.1 to 6.5
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