Another quick followup – last night I set to ruling out one possible cause – a disrupted nitrogen cycle.  In looking at the tank, I honestly had no reason to suspect any actual problems, except of course this recurrent cloudy / infected eye issue occurring with both fish now.  One possible cause however, could certainly be the presence of elevated levels of ammonia or nitrite.  This could easily be explained by the 2 recent rounds of treatment with Maracyn & Maracyn II in the tank.  Part of me would’ve been very happy to find either, because it would give me a likely cause to latch onto and deal with.
Of course, ammonia and nitrite tests both came up with nothing; both tests showed 0 ppm, or basically undetectable levels.  I still decided to dose the aquarium with a full treatment utilizing Dr. Tim’s Nitrifying Bacteria; I had a lot leftover from the initial setup of tanks for Banggai Rescue.  The thought process is this; we may simply be looking at “negative” bacteria levels being elevated, and possibly we can “push out” or displace these bacteria with more “friendly” strains and types that are beneficial to the system.  There is no doubt that the tank HAD to have been compromised in some capacity during the anti-bacterial treatments; in every respect I see no downside to trying this.  I had been thinking about it for a while but honestly can’t remember if I did it or not prior, but I’m able to go on and definitely say I treated the tank with this product last night.  I should also mention that I used this product with perceived good results for Banggai Rescue’s tanks; I can honestly say that I did not confirm the existence of a single tank out of 12+ going through a cycle.  In other words, this product appears to fully make good on its claims to instantly cycle and establish a new tank.  While the price tag is far more than other competing products, there does seem to be a genuine difference (whether that difference justifies the increased price, and whether this works better than competing products like Seachem’s Stability  is certainly something I cannot say without actual scientific testing).  Overall, I’ve come to learn that Dr. Tim’s has an excellent reputation in talking with some other aquarists whose opinions I trust, and those unofficial endorsements and other experiences seem to bolster my own.
As of this morning, the eye is still cloudy…