Get some of each of these dyes and see if they even fluoresce. If they do not this is a non-starter. Even though RG590 absorption peak is around 520nm, the broad UV to blue of a florescent "black light" will make it fluoresces strongly. This would be a fast and cheap screening test. If it fluoresces, then the spectrometers will be worth using. Dyes can be very dense and potent by absorbing well, the rest of the spectrum that they do not absorb. They need to fluoresce ie store and release red shifted energy to create an inversion.