Hello, with the fish with the missing fin, as long as there is enough of the fin filaments left it will grow back. To help ensure growth and also to keep from infections from happening you will want to keep the water pristine.
For the molly if you can provide the following information. Also for trying to get a good picture, if it is proving too difficult in the tank you can always take the fish out and place them in a small clear container filled with some aquarium water. This will give you a better chance of getting a picture of what is going on.
1. Size of tank?
2. Water parameters
d. pH, KH and GH?
e. Test kit?
4. FW (fresh water) or BW (brackish)?
5. How long the aquarium has been set up?
6. What fish do you have? How many are in your tank? How big are they? How long have you had them?
7. Were the fish placed under quarantine period (minus the first batch from the point wherein the tank is ready to accommodate the inhabitants)?
8. a. Any live plants? Fake plants?
b. Sand, gravel, barebottom?
c. Rocks, woods, fancy decors? Any hollow decors?
9. a. Filtration?
10. a. Lighting schedule? What lights are used?
b. Any sunlight exposure? How long?
11. a. Water change schedule?
b. Volume of water changed?
c. Well water, tap water, RO water?
d. Water conditioner used?
e. Frequency of gravel/sand (if any) vacuumed?
How often are they fed?
13. a. Any abnormal signs/symptoms?
b. Appearance of poop?
c. Appearance of gills?
14. a. Have you treated your fish ahead of diagnosis?
b. What meds were used?
15. Insert photos of fish in question and full tank shot if necessary
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