Welcome. Now we have Australia represented. A couple Asians (from Asia), and a Russian and we'll be fairly whole.
I came across some tissue sample results years ago and saw sulfur content far exceeding (by proportion) the typical sulfur content in most hydro nutes. I then delved into my favorite hydroponic book "Hydroponic Vegetable Production" (a MUST for any hydro grower...THE textbook for college level hydro classes). It stated that sulfur problems typically started with slowed growth with no outward signs (leaf discoloration, necrosis, etc...). I took this to mean that you could be low on sulfur and never know it. At this point in my growing life there were like 2 hydro stores in the whole Los Angeles area. Foothill Hydroponics was my store. They made their own nutes and carried everything to make your own as well. I started adding magnesium sulfate and my growth exploded. Also, my plants stopped turning purple late in life (low mag...I thought I just had some kill purple shit). If you check the lables on Botanicare Sweet, AN Bud Factor X, Cutting Edge Mag Amp, and several other nute additives, you'll see that the ingredient is magnesium sulfate.
In time I found out why these 2 elements may be lacking in some growing techniques. Organic matter is loaded with sulfur. There's probably enough sulfur in a pot of FF Ocean Forest or Roots Organis potting soil for the life of the plant. In fact, just about any potting soil probably has plenty. Therefore, it wasn't something early fertilizer makers worried about. But, when we go inert medium, we have none. Since slow growth is the main sign of a problem (if there's a serious sulfur def, other signs appear), people may not even know that there's a problem. Most older basic hydro nutes weren't made for CO2 pumped, massively lighted, turbo charged pot plants. Hence, the additives. To this day, the only additive I use all the time is magnesium sulfate...currently Cutting edge Mag Amp.
Magnesium is present in large quantities in tap water. Back in the day, very few growers used RO units. Now, they're the standard. I have been using them for most of my growing career. 20 years ago they were so expensive that I leased mine! It was like $50/month and a company came out and serviced it every few months. Anyways, the old school nutes counted on the mag present in tap water. Now that we use RO water, extra mag is needed. If the hydro companies put too much in the basic nute, and the grower used tap water, there would be mad toxic problems. Hence, the "mag" in the magnesium sulfate additives.
I confirmed all this in an in depth conversation with a rep from Cutting Edge (my current nute of choice). I was asking him how necessary their 3 additives were. He said 2 were optional, but the Mag Amp (magnesium sulfate) should be used always. Hopefully the nute companies will reformulate their basic nutes with enough mag and sulfur in the future. However, don't hold your breath...they make alot of money on additives. Many people think the additives are some magic voodoo. In fact, they're just giving is the rest of the mag and sulfur that should have been in the base nutes. Since low sulfur problems just cause slowed growth, it appears that the base nute has everything in it (if it caused leaves to die, people would never buy the base nute). Low mag usually doesn't show itself until late in bloom. I used to just think it was the plant winding down, or some sort of purple strain. The point is, the base nute works just good enough to make us think it's got everything. But, then we put in the additive and are convinced that the "secret sauce" is some magic growth booster. Here's the kicker: A gallon of one of Cutting Edge's base nutes (either Micro, Bloom, or Grow) is about $25. A gallon of Mag Amp (the rest of the magnesium and Sulfur) is over $100!
Is it a conspiracy? Am I just paranoid? Who knows...and who really cares. When I add magnesium sulfate my plants grow WAY faster and stay green and perfect right up until the flush starts yellowing them. If you want to give some a try, the Botanicare Sweet Raw is the cheapest.