Topdog has loaded you with some good info, ill just add a bit of input
Try not to water SEEDLINGS directly onto the leaves, as it is bad practice and the SEEDLING uptakes its needs through the root system (its ok with plain water but nutrients will burn the leaves, when you clone however the clone rely on you watering the leaves as they cant use their root system which they do not have right away) I only say that because I saw drops of water on the plants.
The size different is nothing to worry about as they are only TINY babies right now, they will both grow to be about the same size so you shouldn't worry too much just yet.
Unless one significantly outgrows the other, then you would have an underlying issue and its not the seeds its probably a deficiency or other problem (which you do not have just yet so don't panic).
Your 1x 100W 6500k will be ok, if you find yourself needing more light later on you can add some smaller light socket 40W globes from any local shop near you, but again before you add the lights make sure they are the right spectrum/size for your stage of growth.
Those will be ready to be transplanted when you can see the root system out the bottom of the current tubs you have them in, this is why many people start their seeds in see through plastic nowadays, just stops you from having to lift the plant up to see the roots.
Also be careful how much you water seedlings as they do not need a lot of water, MAKE CERTAIN the top layer or so of the soil is dry to the touch and not moist before watering again.
give enough water to WET the soil as the plants have no care for swimming
Sorry for making you read so much