Yes very doubtfull the dealer laced your pot. However you are right. Better to produce your own. The gardener may have used heavy pesticides, pgr's, had a problem with powdery mildew, ect. Your only doing 2 plants. That tells me small space and or small light. Nutrient manufacturers write the directions with the assumption that your useing 1000w or there equivlent in leds (700w or so if red, white, and blue 550 to 600w if its a cob), or cmh (630w) If you have less light use less nuts. If your a beginner switch to an organic nutrient and use distilled or ro water. You will never have a ph problem again. For 2 years i have used ocean forrest and the entire roots organic master 5 mil feeding scedule with ro watter. I feed every watering after the first month from seed untill the last week they get ro water only. Never once have i even tested ph, much less had a problem with it. Btw. Whoever told you your plants were toxic is smoken crack themselves. The first sign is burnt tips. Ph being off wouldnt effect that anyway. Ph effects which nutrients are available to the plant. The ph being off a bit causes nutrient deficiencies. I run a hydro store and the first thing i tell people who come in saying there deficient in something. The first thing i tell them is to test the ph. If the ph is way off the plant will start to wilt as if it needed water because the plant cant pull anything up. This also happens if there is to much salt built up in the soil.