The frequency of light is important for plants. IMO, the actinic part of the 50/50 bulb wont be doing much for the plants. I may be wrong, but everything I've read indicates a 65k - 10k range is more in-line with what plants need.I'd recommend researching your type of bulb online to find out its specs.
Also, if the lamps have been used, depending on how long, they may need to be replaced anyhow ( most people say after a year the spectrum of light being produced is really degraded ).