Can anyone please advise if my autoflowers are the...

Yeah, they're pretty small but don't give up! I would move your light up higher... 24" from the plants would be good... and give them 100% of the light (autos, once they've been "hardened off" to light, will take a lot of it without harmful effects. They also need a lot of humidity around them at this stage - it's pretty much the only way they get water since the root system hasn't really gotten off the ground. I like to wrap a wet towel around them in a circle so the ambient humidity is very high ... After a week or so of that, and when they get another set of leaves on them, you can let them fend for themselves in the humidity the entire tent gets... which should be around 60-65%. Don't start feeding them for at least another week but when you DO start feeding them, introduce the nutes slowly - i.e., at about 1/4 strength to start off. The biggest piece of advice I would have for you is to introduce some microbes into the soil... these will help grow the root structure... once a week feeding of microbes is all it will take (don't give it to them more often than that at any stage of growth). I think you'll start to see these little ones take off pretty soon and I wouldn't worry too much... make sure your water is pH'd properly, add some microbes, pull your lights up a bit, relax and enjoy the journey!