Healing node boost don't increase the pest node heal (or if it does, I'm not aware of it) but having multiple sources of healing in one team is good. Add a Chocolate Cosmos/Lantana somewhere in your squad and your Lavender/Edelweiss pair will be good for stage with a lot of small pests or with pests dealing tons of damages (there was an event like that, with pests dealing like 6~8k damages in one hit).
Okay it's not that good, espacially when you have some high level rainbows but that's still better than nothing.