Yeah the temp is fine. You should continue treatment usually a week to two weeks after you see the last white spot. So you can keep the temp up just fine, your cories might become short lived after a while but it's not like they're going to die tomorrow or anything, it just won't be the normal 2-3 years they live or whatever it is. I don't know exactly how long they're supposed to live.
So since they still have white spots I would look into some Kordon Rid-Ich or Ich-Attack, easy to dose and I used 2x the amount for my 33, so I was using 6 teaspoons at that time every day with the water changes. But since you're still seeing the white spots I'm wondering if it's one of the strains that is resistant to heat....either way I think it would be good to invest in some least stressful medicines like the Kordon stuff. That worked really well for me and my girls and no one seemed effected by it negatively. it's also safe for plants and inverts too so that's a plus!
Leopards: 1:4 Hawkeye, Luna, Astrael, Dorian, Cullen