First grow

Really rough start, lost a few seedlings due to over stretching and not recovering. Growing medium is coco thats been washed and buffered with calmag. These 2 stayed short but I think I let them go without nutrients for a couple days too long. Started feeding yesterday at 1/4 strength. One has white tips on its leaves, hoping it was just from lack of nutes. Tried to use the hlg550 as a seedling light and I think it overstretched, and then I put it too close for a few days (dialed down to 50%). Started some more seeds, they are on day 2 now from sprout, under a cheap LED light, will put them under the big light in a few days? Definately think the 2 GSC were stunted compared to similar timelines ive seen, I think these are like day 10 already lol. Going to feed nutes earlier to the 3 seedlings and be more careful with stretching. I have the light at around 19" from top, dialed to about 60%, hope thats good. I have a lux meter coming to try and match some lux readings from other grows just to get me in the right ballpark hopefully (no par meter). TDS runoff from this feeding was 350. Tap water left out overnight has a TDS of around 170.