How cold did your garage get?? I also overwinter a ton of subtropicals in my garage (including the Sago palms), but make sure the temps do not fall below freezing. If you garage was dark, the plant also burned due to it not being acclimated to an already potent March sun (despite the chill). This plant in not cold hardy in zone 6 without some serious winter protection. I would put it back into the container and keep it inside until milder weather--keep it on the dry side until it resumes new growth. The plant may loose ALL its leaves but still has an excellent chance of coming back. I had one that I took for dead only to have it suddenly push a new crown of leaves. These are pretty robust, strong plants that want to stay around for centuries--but you're pushing it to the limit. Good luck!

I've got several clumps of them growing and occasionally stems/trunks get broken by falling branches or fronds. Those stems never re-sprout except from the base. They're a clumping palm but are fairly slow growing. Eventually they will be tall. I've never tried cutting out stems to force new growth but it should work okay if the plant is healthy. When you say "they'd like it to look healthier", does it look sickly, or are they just concerned about it looking spindly? Because, spindly is what that species looks like, it's not a question of health.

It's normal for older leaves to yellow and die off, as long as you're getting new ones at the top. When it comes to watering it's best not to go by regular intervals. As weather fluctuates water evaporation rates change as does plant up take of water. You need to check moisture in the soil and water as needed. It's best to have fast draining potting soil as then it's more difficult to actually over water the plant. You can also give it an occasional good flush with water to prevent build up of excess mineral salts from fertiliser. I'd use the slow release fertiliser when repotting, they don't need a lot. With the vagueries of Melbourne weather I'd be careful about leaving it out all the time this time of year. (I'm in Darwin but know how it can be down there). The Bamboo Palm is Chamaedorea seifrizii and it's a multi trunked palm, so it will keep growing more trunks/stems (I have some with stems over 4 metres long). The Parlour Palm is Chamaedorea elegans which is a single trunked palm. So you have multiple plants in that pot. Due to competition from so many of them growing crowded together you'll have to expect some of the weaker ones to die off. That's normal. Otherwise, they're a good indoor palm and fairly slow growing. They can get up to a couple of metres tall, but you won't have to worry about that for quite a while.

duplicate post : https://www.houzz.com/discussions/6054633/can-someone-please-give-me-tips-on-how-to-save-my-bamboo-palm#n=1 lol.. i thought you had 2 ... until i finally realized the mirror .. lol ... i was going to try to figure out if one was doing better than the other.. which might indicate a pot problem ... lol