If it has been 6-7 months and nothing was added since, it is unlikely it is disease, although ich can be hiding in many tanks. Please do not use any copper related medications or any of the cure all meds many recommend. Whether you agree or want to hear, liver damage almost always occur from these meds. Even ick would be unlikely because it would have had to have a blood host, and the shedding ability makes it very hard to attach to a healthy lion.
Check water parameters and make sure there had been no ammonia spike. Raising mg to 1600ppm can address many digestive issues.
How often and what have they been eating, not eating for a week is really not long for a lion, especially if they have been fed too frequently. This is also where mg helps. This 6-7 month metric is where issues arise from pre-existing chemical poisoning, yes including coming from sources that use copper. As well as dietary deficiencies arising from a diet high in thiaminese and/or too low in proper fats.