aside from possibly missing earlier symptoms in the oscar, I have no immediate idea. your tank & other fish look very good.
Have you seen the oscars' poop appear normal? (before yesterday)
Do you have a water changing schedule?
Do you treat the new water with something, and what product?
Oscar died already
Does it typically go that fast? He seemed perfectly fine yesterday morning.
Considering the speed at which the oscar died, Yes, treat for IP's and ick at same time. Although he may have struggled longer than was obvious, I would be very proactive in case there's an unusually aggressive pathogen.Since I'm dealing with internal parasites and most likely ick...what plan of action should I take to treat the tank? I already started raising my temps last night to get them up to 86-87 to hopefully kill the ick, but should I treat for IP's at the same time?