[X] Approach Lord Farring as yourself.
-[X] Reassure him he is not a direct target of any Maester conspiracy, though you don't outright deny they aren't working some intrigues, you don't blurt details other than the fact that his wasn't trying to work any sorcery like what occurred with Jon Arryn's child, which was deliberate.
--[X] If asked to elaborate on this--and fair enough--you aren't sure what caused Jon Arryn's son to grow older all of a sudden, but you know it wasn't just some tricksome Fey's plot without purpose or for some kind of poetic irony, hence calling it "deliberate".
--[X] And as for "what intrigues" the Maesters might be working, you point out that it is vanishingly unlikely even a tenth of all Maesters could be involved in a single group of schemers, given how factionalism works in the Citadel, and the fact that the majority of Maesters, if they do happen to be involved in these plots, are likely totally unknowing.
--[X] The problem with the Maesters isn't so much that there are people using their influence to work treachery all while holding the trust of Westeros' Lords, it is that with all of that, even if the vast majority held to their oaths faithfully, it would be trivial to abuse this symbiotic relationship and turn it cancerous. It would take drastic measures and reforms to cease this business, and even naming a fraction of what you know of does nothing more than make him a target where right now he is not.
--[X] Essentially: Let Viserys be the visible target for that ilk.
---[X] If it helps at all, Jon Arryn's death as far as you can tell was completely mundane, confirmed with divination and cursory investigation. The man was old. He was old and took a bad fall. It's the most common death for noblemen disconnected from the usual avenues for "untimely ends". A regular ride through the countryside, not even during a hunt.
---[X] "My Lord, you are surrounded by a hundred conspiracies, but I doubt many of them have you at the forefront of their plans, and you are likely just an incidental piece on the board of various players. Such as it has ever been in Westeros, and with only leal servants and trustworthy allies warding off the most common malaise infecting the realm." Take it from a man who is the target of about half of those secretive cabals, basically.
