Auto Northern Lights in coco/perl

Day 36 - 25.4*C (77.7F), 62% RH. Rotated the main stem + re-applied some ties. Fed 1.5L @ 1142ec, 5.7pH. Got 60ml runoff @ 1142ec. Plant 15cm tall (6 inches). Day 37 - 25.8*C (78.5F), 58% RH. Fed 1L @ 1128ec, 5.76pH. No runoff Day 38 - 26.3*C (79.3F), 63% RH. Rotated the main stem, applied extra ties. Fed 1L @ 1125ec, 5.76pH in the morning and 1L @ 1163, 6pH mid-day (solution mix - 0.5L filtered de-chlorinated water, 0.5L RO + 0.2Ca, 0.2Mg, 0.6Micro, 0.9Gro, 0.3Bloom). Got 90ml runoff (9%) @ 950ec. New growth leaves look like they're getting a little yellowish and the tips are yellow. I'm pretty sure it's a sign of overfeeding. I can see one or two white hairs on the main stem which are still tiny so looks like the plant is getting ready to Pre-Flower. Changed the location of inline fan to get better air extraction so hopefully the temperatures won't creep up anymore. Day 39 - 24.6*C (76.3F), 61% RH. The light was ~ 36cm from the canopy at 90% power (676ppfd) which I think was a little too strong for the plants. I placed the light 46cm from the canopy at 100% power (~550ppfd). Fed 1L @ 1113ec, 6.08pH. Morning feed - 1L @ 1113ec, 6.1pH (0.4Ca, 0.3Mg, 0.5Micro, 0.6Gro, 0.3 Bloom) with no runoff. Evening feed 1L @1080ec, 5.9pH. Got 350ml runoff (35%) @ 873ec. Day 40 - 24.6*C (76.3F), 67% RH. Rotated the main stem, did more LST. Fed 1L @ 1025ec, 5.9pH. Day 41 - 24.7*C (76.5F), 65% RH. Fed 1.5L in the morning @ 1040ec, 6.08pH. Second fertigation mid-day - 1L @ 1040ec, 5.94pH. Got 242ml runoff @ 820ec. Nutrients per 1 Liter - 0.3Ca, 0.2Mg, 0.5Micro, 0.6Gro, 0.7Bloom). I'm also using 1:2 ratio of filtered water to RO water. Starting EC is around 160. Day 42 - 23.3*C (74F), 68% RH. Each top has 2-4 white hairs sticking out. Fed 1.5L @ 1062ec, 6pH mid-day. Got 60ml runoff @ 605ec, 6.63pH (pH has dropped from 6.8-6.9 to 6.6-6.7 range).