Capacitor replacement
They are film type capacitors. Likely any plastic film part (eg. polyester aka Mylar) will work (assuming the value and voltage ratings are the same - or better in the latter case).
For example, 5nF 250V for the middle one.
5nF is not a common value, so you could probably use 4.7nF or use two 10nF in series. 4.7nF is almost surely acceptable. I don't see tolerance markings on the parts, but if it's 10% then a 4.7nF 5% part is within spec.
If the parts are not (electrically) leaky and are within spec capacitance-wise there is little reason to change them. They do not have a wear-out mechanism and those ones appear to be molded.