Spots near ends of leafs

Can anyone give me some insight into what these spots could potentially be? This is a purple punch from Barney’s farm in its second week of life. I transplanted from a solo to 1gal yesterday and noticed these spots. They are only on the 2 bottom ones and nowhere else. The rest of the plants looks great. It’s been in a mix of happy frog/perlite in both the solo cup and 1gal. I’ve only been giving it water and root microbes pH6.2 so far. It’s under an HLG100
Thank for any insight/advice!

Anyone have any ideas? Since taking the pic and posting the spots are traveling up the leafs and now on both sides :/

Why did you transplant so early? I’ve never used the stuff but the number of burnt seedlings in FF soil on this site is unreal.

I noticed a few roots starting to poke out of the openings I cut on the bottom of the solo cups. I’ve burnt seedlings with ocean forest but have had decent luck with happy frog early on