I blended the potting soil with 50/50 sphagnum peat moss/moisture retaining potting soil for my Majesty palm. It feels kinda light and the palm is a little loose in the pot. Should I add more potting soil or should I just leave it how it is?
Just using the moisture control mix would have been better. Here is the ingredient information:
Our potting soils generally contain peat moss (the major component that is harvested from natural peat bogs), compost (the compost may contain animal manures, composted leaves, grass clippings, and/or composted bark), and perlite (white volcanic rocks used for drainage and soil texture). Some contain Osmocote fertilizer that look like small clear fluid-filled balls.
The Miracle-Gro Moisture Control Potting Mix also contains composted hulls of coconuts to help absorb more water than regular potting soil. This is the Aqua Coir (pronounced "core") component of the soil.
Adding sphagnum peat moss 1/1 was unnecessary, and if you just repotted recently, I'd recommend doing it over again with just the mix. Light mix is good for a palm, but it won't thrive in 1/2 sphagnum peat without a lot of fertilizer frequently, as it will tend to run right through.