Epsom is great for peppers provided your soil needs it.

Definitely if new leaves are curling or foliage is pale.

In past years, I've sprayed all the leaves everyday for a week (1 tsp per quart of water) when needed, but this year I have more plants so if I see new growth curling, I'm going to add epsom salt to the watering can. Hadn't thought to add to the soil. Will research it.