It's really hard to see any detail in those photos and I have never grown anything with lights but what I can see is that the seedlings are extremely tall and leggy ie very etiolated. This is a sign of being grown with too little light and, probably in this case, too much heat.

I Googled the rapid start stuff and it seems to be a product for hydroponics. Seeds started in a seed medium don't need any additional potions until they are up and growing.

I can see spinach, cabbage and Brussels sprouts labelled which are all cool season crops which could be germinated with no extra heat at all at this time of year. You have mixed them with peppers and basil which require much higher germination temperatures. All in all I am afraid you have just tried too hard with these seeds. Most of them would have germinated and grown well if sown outdoors, either in the ground or in containers for transplanting. Can you tell us what the seeds are and why you decided to start them indoors under lights in the height of summer? It is an odd time of year to be starting basil and peppers. Even for the brassicas it is probably too late to be starting seeds for winter greens. (Although I don't know your climate.) Are you going to be trying to grow these vegetables indoors over the winter?

@floral_uk z.8/9 SW UK Thank you so much for the long and thoughtful response. I appreciate your feedback and time.

I have done some research and I believe I made a few mistakes. One of them you nailed. The light wasn't close enough to the dome to start which made them leggy. I have rectified that by moving the light to as close to the dome top as possible. I also am going to be using a higher output light (going from a 14w to a 45w version).

The Rapid start stuff came with the seedling hot house kit. I am starting seedlings to be used in hydroponic systems. The medium they are in is called Rapid Rooters (https://www.amazon.com/General-Hydroponics-Rapid-Rooter-Replacement/dp/B0002IU8K2) that are generally made for hydroponic applications.

The colder water items, like cabbage, brussel sprouts, spinach ect are going to be outside in a hydroponic system out there. I also have raised dirt based beds which have winter veggies in them mixed with end of season things like tomatoes, green beans, ect. The other items such as basil and peppers, I will be keeping inside in hydroponic systems and growing in the warmer garage (or trying :).

Last night, I tossed all the seedlings except for the thai basil and the thai peppers as they just germinated and were not leggie yet. Another issue was too much humidity which caused the white fungus to grow everywhere. I have lowered the heating pad thermometer down to I cleansed the trays with a diluted hydrogen peroxide solution before putting the plugs and seedlings back in. I will monitor closer (when I can and I am not at work) and allow more air flow through the seedlings. Also, I will not put as much water in the tray. I think the goal is to keep the rooting medium moist but not have excess water in the tray?

Lastly, as soon as they germinate and are starting to poke up, I hear I should remove the humidity dome. Is that true?

Yes - you should remove the dome as soon as you have germination. That is one reason why it is not a great idea to mix different seeds in one set up. They will germinate at different times. All the rest of your set up and methods is way beyond my understanding or experience. I suggest you go on over to the Hydroponics Forum which is where the experts hang out.

Thank you. The hydroponics forum is unfortunately rather slow. Not a lot of activity over there and other places that deal with hydroponic gardening is usually dealing with marijuana which I am not the least bit interested in.

Question though. When you water your starters, do you leave a level of water in the bottom tray? Or do you water just enough to keep the grow medium moist?

I appreciate the feedback :)

I never leave trays or pots in standing water. I keep everything as simple as possible and have never used lights or done hydroponics. You might find help on the growing under lights forum or even the vegetable gardening forum.