hm. I beg to differ on the action of epsom salts on the chemicals in the soil.
Epsom salts is simply an inorganic magnesium source; specifically, Magnesium sulfate. In aqueous solution, it dissociates into its components, Mg+ ion and SO4- ion. Sulfate has an equilibrium with sulfuric acid, just fyi. Adding epsom salts will actually ADD to an existing lockout situation.
The only thing that will help to remove built-up chemicals and locked salts from your soil is a chelating agent (or a strong acid, but this is not an option for obvious reasons, lol). Chelating agents are compounds that keep individual ions from recombining into undesirable salts. Humic acid, oxalic acid, EDTA, and EGTA are examples.
Flushing with such a strong solution of epsom salts is something I would not personally ever do. If I saw a deficiency, I would apply it as a foliar spray, and at a MUCH MUCH lower concentration. As a fertilizer, even for roses, who love it, a couple pinches scratched into the soil surface is more than enough.
Ammonia in its only form is fully soluble in water. The reason that it makes your medium acidic is that it, like epsom salts, has an equilibrium with an acid, in this case, ammonium (NH4+). The nutrient problem is that it is, as a Nitrogen source, TOO available to your plants. Nitrogen overdose can lead to weakening of the excessive new growth and susceptibility to disease.
I don;t see a need to flush those plants, but you need to take better care that they do not run out of water in your hot, arid climate. This IMHO is the primary reason that they are not as large as they could be.
In general, they look great.