Too much sun too quickly. You're lucky it didn't burn worse. I have found from personal experience that this palm's cousin, the spindle palm, burns even worse when exposed to direct sun without sufficient acclimation to being outdoors. I put mine into relatively heavy shade for a couple of weeks before increasing the intensity (depending on the species). Still, your palm will eventually grow more normal leaves (the discolored ones will not change back). Also keep in mind that bottle palms are super tropicals so watch those temps.

Yep, looks like somebody forgot to apply the sunscreen.

definindtly sunburn

Sunburn

How did you overwinter them?

Next time, apply some SPF35 :-)

I overwintered them in my garage in front of a window. Probably 4+ hours sunlight each day. I also left three flourescent bulbs burning 24/7 to provide light inside the garage area.

Is it okay to have light on them at all times?

I'm going out on a limb here,sunburn?

Okay guys I get it. I thought that the (limited) direct sunlight it received would not be too much. It had already been taking on 4-5 hours sunlight each day near from my garage window. I guess I was wrong. Next time I will set them out on the porch and move them more gradually into full sun.

I tend to be really bad at acclimating my palms. I have a near 4 foot Roebellini that got sunburn last summer. I took it from inside the house and placed outside on the east side of a brick wall, where it only gets sun from sunrise until about noon. The only leaves that got sunburn were those furthest from the wall, the ones that got the most sun, but I guess I should have acclimated it better. I get really lazy with acclimating because I have so much stuff. I put my oleanders out, and just let the old leaves fry off in the sun. Within a few weeks, they completely regrow anyway and start to flower like crazy by June.

There's nothing wrong with the fluorescents on 24-7 but the light is so weak it is of little benefit. And sun through a garage window during the winter when the intensity is low, isn't strong either. Also, lack of good air movement indoors also seems to "soften" plants.

The only reasonably good source of artificial light would be HID. I have a 150W spotlight MH lamp above my big bottle palm while it is inside and it does the trick. The light is intense enough that when I bring the plant back outside it gets acclimated quickly.

Well, lesson learned, next time give your palms a few weeks to gradually get used to the outdoors.

The best way i have found is to put the larger palms in the front and let them shade your others.