After planting Washingtonia Robusta trees (7-8 days later) started browning ends of foliage and yellowing a lot.
how often are you watering?
Mine took a month or so to become accustomed to its new location. Let the fronds yellow completely before trimming. As mentioned previously don't over water. Were they pot grown?
The Washy's arent accustomed yet to the new location. They will be in shock for sometime until they are established. No worries, just dont try to over water. You'll be ok.