Could be sun burn or spider mites. The holes are probably snails or green worms. Pick off the discolored leaves and mist the underside of leaves to see the tiny green worms wiggle. They are hard to spot when they are tiny. The epsom salt helps with greening them up if its a deficiency. Blast the underside of all leaves if you can every day when you water. Spider mites don't like it.

The holes look like slug/snail/caterpillar damage but the discoloration looks like a deficiency of some sort to me. I'd give it something with trace minerals. ES or ironite sound good and I would try one or the other. I'm not sure if both can be used together or if that would be overkill. If the problem persists I'd try something that also contains calcium. I use a product called CalMag Plus which works quite well.