I would almost venture to say that the water change you're doing is too much. I have a 40 gallon and I only do 5 gallons a week. Next question, did she and what is/was the Specific Gravity of the water you used to change it. Right now, I would stop what you're doing to combat the red algae problem. Reason being, you yourself aren't the one who is dosing this medication, and you aren't around to watch and be ready for things to change. Someone else, the wife, has very little to no knowledge most likely on saltwater tanks. No offense to either of you. You might want to give us the name of the treatment you're using as well.
Another thing you haven't mentioned is your temperature. Perhaps maybe you're Heater coincedentally decided to either stop working all together, or get stuck on, thus "boiling" the tank. Another possibility is that you're house temp is too great and the tank got too hot. Temperature and pH seem to be the most two important things when it comes to keeping fish and other live stock alive.
Your big water changes can be detrimental as well. Yes, it's always better to dilute things as much as you can. But, at the same time, the water you're taking out has microorganisms and bacteria that turn waste into less lethal chemicals in your fish tank. When you take these out, you have a better chance to create what's known as a mini-cycle, which you may have done since your ammonia is up a little. Reason it might only be a little is because of the dilution from your water changes.
If I were you, I would do the following:
1. Stop the Red Algae treatment for now.
2. Stop with the HUGE water changes, let things even out a bit.
3. If its possible, set up a QT tank, get the fish that are left and put them in there. Try not to stess them if you can. Things like catching them at night can help this too. Or use two nets, one small-med. size, and one large. Make sure they're both black. Use the smaller of the two to hoard (yes I used this word with fish) the fish into the bigger net. Try not to move the bigger net if you can. This will trick the fish into thinking, "oh look, a place to hide". Lots of fish stores use this method.
4. Leave the tank fishless for as long as it takes for your fish to start looking healthier.
5. When you go to buy more fish, keep the end number under 4 please! And only add 2 at a time. (It's hard I know)
One question: Is there any chance of a chemical that shouldn't be in the tank got in there? i.e. - was someone cleaning around it and spilled something? That can be another huge impact on your tank as well.
Let us know.