I don't feel this represents Fire too well. it's basically a healing card, with small CC. I'd made give it a Burn effect. Make it like poison, but only lasts 3 turns and stacks. I know burn would be like a weakened poison, but keep the +0/+1 effect for fire creatures that are targeted, maybe make it +1/+1, or +1/0 since fire is all about power. Basically, non-fire creatures targeted by this get the burn effect.