Sounds like you have the beginnings of pythium (root rot). Ice blocks will work but it will dilute your solution as they melt, which could be good or bad. I've been using water frozen in 2 liter bottles to keep my temps down. Its sort of a hassle, and you have to swap them out every 4 hours or so and since they take like 12 hours to freeze, you'll probably need to have a rotation of about 3 or 4 of them. But your only other option is to get a Coolworks Ice Probe because the max temp your res can be is 75 or the roots will rot and your plants will continue to suffer.
dejayou30 Reviewed by dejayou30 on . leaves turning light green to yellow hi all i hope you can help i have 6 plants, since day 1 4 of the plants have a few leaves turning lighter and lighter green with dark green veins some leaves have a burned tip and edge, the leaves are straight except very tips bend down they are 2 weeks into 12/12 E-indoor or outdoor - indoor 5x9x8 sealed, 6in exhaust fan, 2-4in fresh air openings Rating: 5