leaves curling at edges

It seems I have been struggling with one plant to keep it from curling at the edges. I'm not sure why it's doing this I thought I had corrected any deficiencys I'm using the General Hydroponics 3 part with 5-0-10 mix and 5ml of magcal per gallon. They get fed every 12 hours for 15 mins. My ph is 5.8 and drifts to 6.2. What should I do next? I have been using filtered water to get ridd of some of the chlorine but I mixed in one gallon of regular non filtered water. I have one plant that is like 6" taller than all the rest it has started doing it on the top leaves so I'm thinking moisture stress but Im not sure now. The tall one is only 8" from the light but the other one at the front is my main concern.

I have been using GH Flora Micro and Bloom for a long time. I would stop using that magcal until late flowering. Its likely that u thought u needed it because ur ph is a lil high. Lower ph to 5.2, let it climb to 5.8 and repeat, if u still see a mg deficiency the plants are ready for more micro. I use 9-0-12 (m-g-b) for full strength vegging under HD lighting and adjust the bloom 1or 2 ml up or down per gallon depending on the strain, and then I use 8-0-16 (m-g-b) for first half of flower with liquid KoolBloom. Second half of flower I use 2-0-16 (m-g-b) with calmag, and powder KB. The calcium boosts trichome production while the KB fattens the bud.

Phelps said:

I have been using GH Flora Micro and Bloom for a long time. I would stop using that magcal until late flowering. Its likely that u thought u needed it because ur ph is a lil high. Lower ph to 5.2, let it climb to 5.8 and repeat, if u still see a mg deficiency the plants are ready for more micro. I use 9-0-12 (m-g-b) for full strength vegging under HD lighting and adjust the bloom 1or 2 ml up or down per gallon depending on the strain, and then I use 8-0-16 (m-g-b) for first half of flower with liquid KoolBloom. Second half of flower I use 2-0-16 (m-g-b) with calmag, and powder KB. The calcium boosts trichome production while the KB fattens the bud.

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Thank you so much

Is it safe to use botainicare ph power low to lower the ph?