I have this Rattlesnake plant that I purchased in July. It was healthy up until a few weeks ago when it started to yellow/brown. Anything i can do to get it back to healthy? I was watering about once a week, when the soil felt on the drier side.

Dry side is not what that plant likes. It likes moist not soaking but moist soil. Moist like a cloth that water has been squeezed out. Since you are in FL it is probably getting enough humidity which it likes. But you also have very strong sun. Place it so it does not get any direct sun.

Watering
People often come unstuck with the Calathea when it comes to its watering requirements and here's why. This plant demands to be moist at all times, but not "wet" or sitting in water.

here is a good care article.
https://www.ourhouseplants.com...

I agree, Rattlesnake Plant (Goeppertia insignis) (formerly known as Calathea) requires bright shade and consistently moist (but not sopping wet) soil. I got two small Rattlesnake Plants about 5 months ago and they are doing very well for me. One is on a shelf in my kitchen and the other is on a shelf in the master bathroom. I put wicks in the bottom of both pots and sat the nursery pot down inside another container with pebbles and a little water in the bottom. I replace the water as it gets wicked up into the soil.

don't let it reach too much dryness. In my homeland they are outdoors, in shade and there is always intermittent rains there. Humidity levels always high, temps nothing lower than 70F there.

So it is such a tropical, humidity loving, grown on the moist side plant.

I have calatheas, and they are alot of work. When taken care right, it's a site for sore eyes. Wipe down the leaves to get dust off them, I read somewhere they dont like that. True or not, I do it anyways as I do not like the dust lol.
As for soil moisture, I say thank you to this handy dandy moisture meter. The house got so dry with the cold that came fast, I'm watering some plants twice a week! Lol. Link below. You can cut those leaves off at the stem and eventually new ones will grow.

XLUX T10 Soil Moisture Sensor Meter - Soil Water Monitor, Hydrometer for Gardening, Farming, No Batteries Required https://www.amazon.com/dp/B014MJ8J2U/