Two questions - Water temps and Additive Strengths

Ok, so I have a problem coupled with a question that has poppped up in my mind. My room temperatures right now are 75-79 degrees, however the temps in my 5 gallon DWC buckets keep getting warm. I've been using ice cubes the past couple mornings, but for the amount I use, well, my freezer doesn't work fast enough. I guess black buckets were good for keeping light out of the water, but they're also damn good at holding heat in. Short of buying an actual chiller (too pricey), is there anything I can do? I went and bought Mylar today, I was hoping wrapping the buckets and covering the lids with that might reflect a bit more of that light (and therefore heat?).

Also, a question on extra nutes. I had just transplanted to buckets recently, and was running the Lucas formula at 1/4 strength with 5 mL/ga each of Hygrozyme, Liquid Karma, and Cal-Mag. Now, since I am running the Lucas formula 1/4 strength, should I also be running the additives at 1/4 strength? I was thinking I could probably run the Hygrozyme and Liquid Karma at the levels I am now, though I may want to back off on the Cal-Mag, since running that at a higher strength then my base formula might create a solution that is too Mg rich and therefore inhibit the uptake of N. Anyone confirm this? I was using the Cal Mag because I am using distilled water with the Lucas formula, and had heard it lack sufficient Mg. All help appreciated!

Insulate your rez and drop in some frozen 20oz bottles.....insulating is the key to maintaining temps. Or check out the ice probe if you can spend $100 thats what I use.

Ok, just read up on the ice probe, and saw it can cool an aquarium 6-8 degrees. Can this cooling be done quickly? Or do I have to leave it in there for a couple hours? My buckets are standalone, so if it's something that would have to stay in there, I'd have to buy 8 of them. If it's a probe that I just put in the bucket and it chills the water that quickly, well then that's something I could really use! I figure I could just cool my water down twice a day, and keep it within an acceptable range...

Any word on the nutes?

Yea just do everything at 1/4 str....the ice probe stays in the rez and cools over time. You would have to add a rez bucket and a recirculating pump. Then hook all the buckets together....or just get a big rubbermaid and use that for multi plants, thats what I do.