Stalk and Petiole coloring

ensure substrate pH is correct. possibly a trace element symptom, but those are rare in soil. (rust colored stalk) Blueish petiolse possibly P-def. But, could also be related to pH 6.8-ish is best in soil. Slightly acidic is the goal. Do this first... then move on to possibly changing nutrients.. . if this is off.. give it a week to see how it reacts to change. Nosedive should not be ignored, but be patient. Takes time for changes to impact plant. watering habits? stick to a wet-dry cycle. allow 1" to dry before irrigating or fertilizing. Try not to leave standing water on the leaves. You'll grow mildew or worse.