It's fairly normal for new discus, particularly young ones, to hide and to refuse to eat when new.
Are you doing anything to lower the pH? If they are Malaisan stock, they will only have seen a pH below 7 in the bag on the way to the shop, so a pH of 6.8 will potentially be stressing them. I'd advise you to look into raising it a little. Contrary to what most Discus books will tell you, Discus grow better in harder water with Alkaline pH, so that's how most commercial breeders will raise them, they grow quicker in higher pH water, so they can get them out the door quicker and not spend as much feeding them up and growing them on
Smaller Discus stunt easily while growing. Until they get to 4", they need a virtually spotless tank, or they usually will stunt. This means daily gravel cleans in a planted tank, but ideally they'd be raised to 4" in a separate bare-bottomed tank before being transfered to the planted tank. The only way a tank with gravel can be kept "nearly spotless", it large water changes and gravel cleans on a daily basis to remove waste, hence why I'd suggest upping water change volume.
Torpedo barbs aren't a great choice with Discus. They are a large, fast moving fish that tend to stress them out. It would be best to re-home them to another tank

Clown Loach *supposedly* aren't a great choice either, but I've never know anyone have issues mixing the two. I know a few that have hit trouble after adding Torpedo Barbs however
The temperature is OK, but would be better higher, ideally around 30c. The only fish that won't take that heat in there are the Torpedo Barbs, so there is another good reason to get shot of them

A higher temperature will speed up their metabolism, making them "hungrier". Also, with the Discus, it will give their immune system a boost, helping to ward off internal parasites and Flukes, two infestations this fish are prone to
So, I'd suggest upping water change volume to 50% daily, loosing the Torpedo Barbs and upping the temperature to begin with.
It looks like my initial worries aren't justified however. All looks OK, there certainly isn't any definite no-no's in your current care. Feeding is going to need work, but that isn't an immediately pressing issue.
With feeding, you want a minimum of 4 feeds a day (once they are feeding), two being fresh or frozen feeds, and the other two being a dry discus pellet. The SERA stuff is OK for the dried. For fresh or frozen food, you will need more verity however. I used to offer "tropical quintet", a type of frozen ready-meals for fish basically, containing five different frozen feeds. I'd offer that at one feeding a day, and then Peas, Cucumber and other "greens" for the ther fresh or frozen feed. I personally wouldn't feed beef-heart as I feel it potentially dangerous to offer long-term. As a grow-on food it's OK, but it contains many anti-vitamins and lots of fat. It isn't a great feed, as it removes the "goodness" your other feeds add. One thing that most will agree however, is that if you offer Beef-heart, you shouldn't offer it alone, it needs to be mixed with other stuff and hence is should be a relatively small bit of the "Beef-heart mix"
All the best
Rabbut