Is this nutrient burn? have pics

This is Purple OG kush inside a 5 gallon dwc. I am using Cutting edge solution bloom, grow, micro. I am using 1/2 recommended strength nutrient and around 6 ph +/- 0.5. Temps are around 75-80 F and 40 humidity. Kinda hard to see but the margin of the leafs are turning gray to black and it looks like it is starting from the newest growth and working its way to the older leaves. Any ideas what this could be. Thanks

dont know but i know hydro ph should never be above six, i heard 5.5-6 is a good range

Im using GH ph kit so its Yellow with a tint of orange and yellow on the kit says its around 6 and orange is 5 so I think its better than 7.5ph my house pumps out.