dude you sure your not getting the bottom leaves wet when you water. And I have only ever seen canoeing (cupping) in very high temps,common with HID. I agree with the above----- stop fucking with them. If you are worried about the soil being too hot, then get a piece of drywall aka. gypsum. Take a spice grater and powder up some without the paper backing of course. Gypsum is very well known for neutralizing salinity, and is inert. Take 1tbsp/L and incorporate with water, or top-dress 2tbsp/gallon and water in with PH 6.5. You cn also add humic and fulvic acids aka organic acids, and these are best known as chelators. They bond and carry metallic ions and make them more readily available at a broader PH range. Less is more when it comes to organic acids. NO MORE THAN 150PPM supplementation per week. Now fulvic acid is best absorbed thru the leaves and humic is the roots.