So basically: the reddish tones are anthocyanins, which are the reason a lot of plants in full sun come in pink, red, or purple (or -toned, at least)! They're produced over chlorophyll for baby leaves, because until they harden off/mature, they don't need to produce energy really — the old leaves are doing that — but the old leaves are also sensing how much light they're receiving (which if it's sunlight, means how much UV radiation they're also receiving). UV radiation messes with everything, and chlorophyll doesn't protect against it at all — but anthocyanins do! So while it's hardening...
Context: this was in response to someone asking for tips on what fish to get for their first tank, or if we had any general advice. As I do, I got wordy.
"How often should you change your water" is a bit of a moot point for me -- I'll change a tank every time I need more houseplant water, and that's a consistent enough schedule that my fish stay happy! If you aren't like me and in that happy balance, though... How often should you change your water?
It's pretty much entirely up to you -- would you rather have two pots with a single plant (which will be two plants, but neither will be as full) or a single, fuller pot? I've done both, regretted both, and loved having done both in different situations!
Separating them will cause minor root damage (no matter how hard you try to avoid it), but as long as you're careful with it, it'll be superficial and both plants should heal quickly from it. Just make sure that both plants have decent root systems before you make the cut (assuming they're connected -- sometimes pots with more than one plant in them aren't connected at all)!