Newbie grower here with some concerns

Hi I just took an interest in trying to grow some herbs from seed indoors. It is winter here in Ohio obviously but I am just experimenting as this is my first time growing and I'm want to get a feel for things before season comes around. I tried planting some Chamomile in a 5.5"x10" flat and the seeds did sprout but I think I spread too many as about 40 sprouts came up and they all wilted not long after. So technically this is my 2nd attempt at growing. I went out and purchased some small clear widemouthed cups (about 4" high) and put 2 seeds in each cup - 10 cups of Chamomile and 10 cups Lavender. They are currently sitting about 6" under a 75 watt long tubed grow light. Also I have planted 3 5" high pots of Thyme (~5 seeds in each pot), they have the additional underpot watering system where you can water from the bottom of the pot.

What I am most curious about is how much do I water and how long to keep the lights on per day for best results. I am most terrified of over watering or under watering as I am very new to this. So I have started out watering with a mist bottle diluted with some Miracle Grow additive and a touch of lime to raise PH every morning. For the underpot waterers I am adding new water to the underpot each day (It soaks up quickly I have no idea how but it does) and I also lightly mist the tops every morning.

The potting mixture I used was about a 4 part mixture of Jiffy Premium Seed Starting Mix to 1 part Miracle Grow time release Potting Mixture. I tested this mixture to a PH of about 6.0 and I heard that the Lavender enjoyed about an 8 so that's why I added a touch of lime to the misting bottle. (Very small amount, I took a pocket knife and took a pinch from the bag enough to cover just the very tip of the knife)

Like I said my main concerns are with the lighting and watering. Any advice would be much appreciated! I can provide pictures if this would be of any value.

Thanks all for your input!
jdb