Stems could benefit from root tabs. Don't go crazy with them though. The suggested use for root tabs is one every 6 inches in a grid pattern.
You specifically said stem plants not crypts/swords. Personally I have found the whole root feeder thing completely overblown. I have and most have grown completely healthy crypts/swords without anything in the substrate.
That being said some crypts/swords might grow faster, not healthier just faster. Who even wants that?