i'd say they are scared of the 'big bad predator fish' walking past the tank. my bn pleco does that if she's near the front glass and i go up to the tank. if i want to get a good look at her i have to approach the tank really slowly.
my other fish would be the same when i first got them, getting scared and hiding when i was near/going past the tank. after a while they realized that i am the food source and could care less if i'm by the tanks.
i do want to mention though, your stock list for that tank needs some tweaking. that tank is much too small to house all those fish full grown, and the gourami (i am assuming it is a regular variety and not a giant gourami) will not fare well once the JD's and the Texas mature. as for the catfish, what species exactly?
i would suggest having just the two JD's in there long term, if they get along with each other (my research has so far said that there should be only one JD in a tank, due to possible aggression towards their own kind, but individual fish personality is a factor too). that's about all that will fit comfortably in a 75 gallon long term. or you could have just the Texas in there, as the Texas will mature at a larger size than the JD's.
what is your filtration, and what are your current water parameters (ammonia, nitrite, nitrate, ph)??