So sorry to hear about Big Boy. How is he doing?
Even though your water looks pretty good, I would do a series of pwc
's over a few days 25% per time at least about 8-12 hours apart, to help get in some new fresh (treated/ dechlorinated) water into the tank.
How often are you doing water changes and how much?
Do you know if the tank water (parameters) are vastly different from your tap water? Just curious.
How old is Big Boy? Internet states appx. 4-6 years is common.
The major option I would recommend is a round of Epsom salt treatment.
The pine-coning is indicative of kidney failure.
More info in link. It helps with the body regulating functions and can help relieve constipation.