Back when I had my shop, a little old lady came in and asked me to go to her house because she wanted to give me her goldfish as it was too big for her.
So I went, and there was a goldfish bowl sitting on the kitchen table, and the gold fish was about a half inch shorter than the diameter of the bowl!
She had won it as a tiddler at the fair, and been told it would only grow to the size of the bowl. DUH!
A goldfish can grow to around a foot long quite easily.
Your fish look in good health and you describe exactly what fish should be doing, active, alert, and in your case, possibly mating :shock: or 2 males fighting for superiority as and when a female arrives.
Overfeeding wont hurt the fish, because they cant be overfed due to them having a clever stomach that shuts off when its full and diverts everything to the "ahem, rear end"
.
If you see long strings of gunk hanging from the back of the fish, thats too much food. Overfeeding WILL pollute the tank very quickly.
If they eat what you put in within a few seconds, add more. If they wander away from the food after a minute or two while some is still there, feed less.
PH colour strips have some leeway because apart from printing error and fading, even every bodys eyes see colours slightly differently. As long as you are no more than one colour band away, I suggest watching the fishes behaviour before making any adjustments.
If they are alert with all fins erect and actively eating food, youre pretty damn near. If the fins fold down, and they start to swim at an angle and stay at the surface, you have a problem.