Hi and welcome to the forum
When you say electric blue, I assume you are talking about Sciaenochromis ahli, a cichlid from Lake Malawi?
You mention German Blues, I assume these are blue rams (Mikrogeophagus ramirezi)?
And you mention reticulated hillstream loaches, Borneo loaches, pencil fish and glass cats.
Are these fish in the same tank as the electric blue cichlid (S. ahli)?
What is the GH and pH of the tank water?
If you have the loaches, pencil fish, glass catfish and rams in with the S. ahli, there is going to be problems for some of those fish. The S. ahli come from hard water with a pH above 7.0, the others come from soft water with a pH below 7.0.
If they are in separate tanks it is not an issue, but also has no bearing on the S. ahli problem because they are not in the same tank.
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Most African Rift Lake cichlids that are bred locally are normally pretty good quality. If you want good stock you can find a cichlid society or an aquarium society in your area and go to their meetings. You might be able to find stock or get leads as to where you can get good stock from.
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Fish that bloat up and get bulging eyes usually have an internal bacterial infection that can be caused by bad food, incorrect diet, Tuberculosis (TB), or other types of bacteria or protozoa that build up in their body and eventually kill the fish.
Bad food will usually affect more than 1 fish every few months so this is unlikely to be the cause.
Bad diet/ incorrect food for the species is usually a bigger issue in vegetarian fishes when they get lots of meat in their diet. Tropheus species commonly bloat up if fed a lot of meat. Red meats are more of an issue than marine based meats like prawn, fish & squid. S. ahli should not have issues with bloating caused by meat based foods.
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If the fish have an internal protozoan infection they usually lose weight over a week or two, do a stringy white poop, they might eat a bit but sometimes stop eating, and eventually die a few weeks after the initial symptoms appeared.
Metronidazole is regularly used to treat internal protozoan infections in fish but it does wipe out filter bacteria so you have to monitor water quality during and after treatment.
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Tuberculosis (Mycobacterium species) are an ancient group of bacteria that infect all birds, fish, animals and reptiles. The bacteria are found in most pet shops & fish wholesalers around the world and can live in aquariums for years and not need a host to survive. They get picked up by fish and settle in the fish's body somewhere, usually on an organ, where they slowly grow. After a period of time (maybe 6-12 months), the bacteria have built up in sufficient numbers and done sufficient damage to a internal organ, and that organ ruptures or fails and the fish bloats up, stops eating, does stringy white poop, sits under the surface or by a filter outlet and breathes heavily, and usually dies within 24 hours of this occurring.
The bacteria grow faster in warm water and slower in cool water, and they have a waxy coating surrounding them that protects them from most chemicals, medications and drying out. Mycobacteria that affect fish have been found dormant but alive, underneath rocks on dry river beds that have not had water for over 8 years.
These bacteria are extremely tough and hard to kill without strong chemicals like bleach or heat (60C temperatures). In aquarium fish they are impossible to treat and you lose one fish here and another one there and you can't stop it.
My guess is your fish have TB. Some people have had success getting rid of the disease from their tank by breeding fish and separating the eggs straight away and hatching them in a clean tank. The disease remains in the main tank but they get disease free fish by separating the eggs and growing the fry up in a clean environment. The fish in the main tank are then destroyed and the tank is disinfected with high levels of granulated swimming pool chlorine. Whether this would work for mouth brooding cichlids, I don't know but you could try milking the females and hatching the eggs in an incubator in a separate tank with clean water.
If you have TB in the tank or suspect you have it in the tanks, you should assume it is in all of the aquariums. You should wash your hands and arms with warm soapy water after working in the tank and avoid getting aquarium water on your skin if you have any open wounds, cuts or scratches on your skin. The Mycobacterium can get into wounds and cause localised infections called granulomas. These start out as small sores that don't heal and after a few months develop into small lumpy growths that weep.
If you have any sores on your skin that don't heal up quickly, see your doctor and tell them you have fish that might have TB (Mycobacteria). Get the doctor to take swabs of the wound and send it off for culturing in a lab. Wait until you get the test results back (in about 1 week) before taking any medication because TB can only be treated with certain anti-biotics, and taking the wrong anti-biotics will only make the problem worse. There are also different strains in the same species of TB and they sometimes require different medications.
Most people with a healthy immune system never develop TB from their fish, but anyone can get it if they have open wounds that get exposed to contaminated water. Washing up with warm soapy water is essential if you have or might have this disease in the tank. If you have open wounds on your skin and have to work in the tank, get a pair of rubber cloves and wear them to stop the aquarium water getting onto/ into the wounds.
