First Grow (Hydro) ~ Some questions

So, got my first grow. I have 2 seedlings, i did a second because i didn't give the first light soon enough and its quite tall and thin, so i got the other as a backup, however both 'seem' to be doing fine. 1st is about 2.5 or so weeks in and the other is about 1.5 weeks in, give or take a little (more on the take side).

Questions!:

PH seems to be a pain in the ass to get right. Im using a basic test kit atm and am trying to keep it in a reasonable ph range (perhaps 1-1.5 under or over the best PH (5.6-5.8). Is there an easy way to manage the PH? The bucket is about 2-3 liters max of water. I noticed the aquarium had a solution to set the water to 7.0 or so, but couldn't see anything for 5.8 and am wondering why this doesn't seem to exist for hydro growers...

How often should the plants be fed? I have the first plant on a timer for 4 times a day (every 6 hours) to have water pumped to its rockwool for 15mins. Is it getting enough water? is it getting too much or too little? The second seedling i am just hand-watering a few times a day, trying to keep the cube damp.

How should my system be set up? At the moment the water sits a few inches below the net pot and the water gets pumped up 4 times a day as said earlier. Should the water level be higher? I have been seeing people recommend to have the net submersed while it gets its roots long enough.

The main 3 points (Ph, feed/watering frequency and water levels) above are my questions at the moment.

Hopefully someone can shed some insight and anything else you may think i could have handy. I have kept the ppm in good ranges (very small nutes for the seedlings) and i know most of the stuff there is to know, i just haven't seen much info on using a bubbler.

thanks/