Salts are in most ferts which is why we are advised to flush the media once a month will plain water only to reduce build up and toxicity. I use Tomorite and Vitax orchid feed (30.10.10 ) high in nitrogen with equal parts potassium/ phosphorus. The tomorite contains seaweed extract which is widely recommended and offers a alternative quantity of nutrients to balance the intake. Fed weekly in weak quantity, alternating each time. I do not feed for 3 months Nov, Dec, Jan. Tried Miracle grow ( blue crystals) but found this burnt roots easily so changed.