What is the exact model number of your lights? Let's see if there's any spectral power distribution chart for them on-line...

Definitely try other papers that are known to be working well with pt/pd process. Also old FO can be freshened by adding small amnt. strong hydrogen peroxide (strong to not dilute the iron solution too much), but that's not the business rigth now - we're not sure it's your FO, that (or buying new FO) would be the last measure.

Regards,
Loris.