Bummer about the leak- hope you're able to fix it.
A few questions for you about heating the tank (You mentioned you were running two 1,000 watt heaters?):
1. What brand are they?
2. Are they able to keep the temps up?
3. You mentioned the water was down to 60 degrees in April...how cold was the ambient air temperature?
4. Any idea how often they are on? I'm looking to set up a big tank but with electrical rates what they are here in CA, I'm guessing it's going to cost me a few hundred dollars a month just to maintain 78F.