Originally Posted by winger
You can save 1 liter of old brown (and replenish with each session if you'd like) and add 50-100ml to one liter of fresh solution. You may have to play with that a bit. The exposure looks good (based on the highlights) and keep in mind that Art300 gives somewhat low contrast results with normal exposures. You may want to try more exposure but only use 10ml each of developer per liter and bump the temperature up to 90-100 degrees. You may get a bit more color and interesting results, although Art300 will still give pretty muted and neutral colors in lith. Paper wise, that negative may look great on Varycon, or even Slavich (but with Rollei Vintage developer) with heavy exposure, dilute hot developer and an early snatch. So many possibilities!
Good luck but that's a GREAT start!