I would say trust your own instinct, if you think he is acting strange, then he probably is, because you know him best
From what you have described, if he is not acting like his normal self, then something must be off. I know they have their moments where they may not be as active and some may even be temperamental, but not interested in food or interacting with you in their usual way would definitely raise a red flag.
The general guideline for your tank size should be at least 50% wc midweek on top of the 100% wc that you already do. I personally would do 2 100% a week. 73 is on the cold side unfortunately, you may want to get a heater and raise it slowly to 78 or so. They won't exhibit any symptoms from the lower temp immediately, but I think overtime, it takes a toll on their immunity and overall health. If you can, try to increase the frequency of feeding time per day, to at least twice a day.
Is that white stuff you mentioned shown on the photo, or is that just visual effect from the light near his eye/mouth? He sure is a "beefy" boy, just like my Lapis. I would say for now, try to do a full change of his water (may be something got into his water) to see if he perks up. Also, take a closer look or photo of this grayish patch you see around his mouth. Just keep an eye on him since you are not able to definitively diagnose him with specific condition. I am sure someone will be along to give you more suggestions/advice.
Good luck and keep us posted!
The general guideline for your tank size should be at least 50% wc midweek on top of the 100% wc that you already do. I personally would do 2 100% a week. 73 is on the cold side unfortunately, you may want to get a heater and raise it slowly to 78 or so. They won't exhibit any symptoms from the lower temp immediately, but I think overtime, it takes a toll on their immunity and overall health. If you can, try to increase the frequency of feeding time per day, to at least twice a day.
Is that white stuff you mentioned shown on the photo, or is that just visual effect from the light near his eye/mouth? He sure is a "beefy" boy, just like my Lapis. I would say for now, try to do a full change of his water (may be something got into his water) to see if he perks up. Also, take a closer look or photo of this grayish patch you see around his mouth. Just keep an eye on him since you are not able to definitively diagnose him with specific condition. I am sure someone will be along to give you more suggestions/advice.
Good luck and keep us posted!