For the 6-day old ones, I'd say they're seedlings and that the label's 1/4-1/4-1/4 dose would be safe. That's 1.25ml per gal. But, label strengths are usually too high. I'd do 0.5 to 1 ml in the first week. But, soils usually have enough nutes for the first week, and it doesn't look like you need to do anything with them. I don't think 0.5ml would hurt. But, I don't think you need it either.
I forget what you said about the older ones, how old they are. Assuming they're in the 1st week after seedling week, I used Useless's "week 1." But, again, it depends on whether your medium has any nutrients built into it. If they're 3 weeks old (Useless seems to start week 1 of veg after 1 week of seedling), I'd start at week one for the first feeding, then move up to week 2. Next week, week 3 (when the plants are 4 weeks from sprouting).
One thing I like about useless is that it directs a new grower's tendency to over manage their plant into something rather harmless. You can fiddle with various proportions, analyze them in the spreadsheet, watch how your plants respond to each week's new NPK ratio (and strength in ppm). It's like a guided experiment for a new grower (instead of just sitting in front of the plants willing them to grow, perhaps meddling and causing problems).
I didn't answer your question about the light-colored new growth. I think it looks normal. It could be a sign of needing nutes. But, it's not too unusual.