if your stems are firm and starting to glisten at the tips, you should be okay. it is thought to be an adaptive characteristic among horticulturists for the new growth to be reddish or burgundy...usually where there is vigorous young growth.

The new growth does not yet have chlorophyll and thus does not reflect the green light of the light spectrum, it also helps protect from herbivores as they will see the red leaves as non-nutritional. This allows the leaves to mature and come online for the plant once they are large enough and have chlorophyll.

The difference between your old and new plants may be growing conditions...ie: outdoors vs. greenhouse growing. Sometimes, nursery growers will keep the young plants in conditions that favor root growth more, instead of leaf/stem development. This leads to a better rooted plant product for them to sell, and also allows them to maximize their growing space...in summary, I would not worry about the red color, most of mine have that color on the tips and in red flower cultivars even the petioles of the leaves, and sometimes the leaves even have red color/tint.

Very informative, thank you! Kind of crazy the difference in color. I have one now that has almost purple/black leaves due to how dark they are (I promise it's not rot...). Plants never cease to keep amazing me.