Im feeding with humboldts secret. In coco coir. I...

increase it slowly and see how the plants react. if its negative then just lower again

You should give what doesn't cause problems. If it happens to be 700-800, that's great. Star with the instructions, but if you get deficiency or toxicity symptoms, you adjust to the reality in front of you... not what 'should be' in coco make sure you are getting 10% runoff each irrigation and fertilizing every irrigation. That's the proper way to use a soilless medium. The exact soilless medium is mostly irrelevant as far as procedure and fertilization. I only feed at 600-650ppm from start to finish with minor tweaks to N concentration in flower. More will end up with problems in the long-run. This isn't foie gras. You can't force feed the plants. Whether it takes a week or 2 months, if symptoms arise, it is the formula's fault in the context of a soiless/hydro grow.

If you're growing in coco coir during the flowering stage and feeding at 700–800 ppm, you're within a safe range, but you could increase the concentration slightly if there are no signs of excess, such as burnt tips or leaf damage. Raise ppm during bloom to around 900–1100 ppm to support better flower development, always monitoring how the plant responds. If the plants look healthy and show no signs of overfeeding, increasing the ppm a bit can help maximize floral growth without issues.

Ich würde sagen auf jedenfall ein bisschen, aber da sind ja mehr Faktoren. Wie ausgangswert von deinem Wasser, Blütewoche, Licht und größere der Pflanze. Ich denk 1000ppm sind kein Problem, wenn die Pflanze hungrig ist. Messe den Drain dann weisst du mehr.