My understanding of UV and far red is that they should be deployed during flowering but only for a short period of time. An hour or two a day. UV and far red together is a good combo but far red on its own should primarily be used to "put the plant to sleep", i.e. during the last 30 or so minutes of the day's light cycle.

Generally speaking, UV and far red diodes emit MUCH fewer photons than 400-700 nm diodes. In my experience, you get more bang for your buck if you put your money into light producing diodes.