The top one is looking like it’s gonna be good just real rough start lol. The smaller one looks like it’s gonna make it as well but it’s not unheard of to have a runt of the litter and that may be what you have. Keep at it and who knows, it may surprise you
. I would be interested in knowing what your test bucket does without an air stone as well, once you see what happens re ph with air stone, I would bet it’s more consistent. I loath airstones and ditched them pretty quick, I found ph was very unstable using them but for the life of me I can’t remember what it did, rise or fall, I’m assuming it fell by increasing the amount of CO2 added. I am always waffling about trying them again but haven’t needed to.