Some modern resistors are designed to run hotter, and can be rated at over 100C. Obviously, this is not good for surrounding parts or for the PCB itself. Looks good on paper, but not good 26 years later. Parts are cheap, and being conservative with parts ratings is just good insurance. Any parts showing signs of overheating should, by definition, be replaced by more conservatively rated parts. Obviously, nothing physically smaller than the originals - lesson learned by the manufacturer?
Resistors also have a voltage rating; within a brand and model, this usually increases with increasing power rating. Little metal-film resistors that fail open, but not obviously overheated, have probably died from exceeding their voltage rating. Again, the cure is a more conservatively rated part.
Your second image, of R111, looks like the resistor is not discolored, but its heat has discolored the PCB. If that's true, you might want to replace the solder in its solder joints. They've been through many cycles of heating-cooling-heating-cooling and their crystal structure is damaged. Easy and cheap insurance.
Electrolytic capacitors age rapidly at higher temperatures, even the good modern Japanese parts your pictures show. When you do replace them, use good modern Japanese parts, Nichicon or Panasonic or something of that quality, rated for 105C.
All good fortune,
Chris