I would be careful with N if the soil is still dry and the weather hot as in that situation you're more likely to get fertilizer burn and the salts can make it harder for the plants to take up water. Epsom salts (magnesium sulfate) isn't necessary unless you have low magnesium. I don't think I would add that in dry conditions either. You're more likely to have low magnesium on an acidic soil and there are better, longer term, ways of dealing with it in that situation than Epsom salts.
