Is my Fish Sick?

[BakedFish]

I have a male molly living in a 20-gallon with 2 small shrimp, a few small snails, a bristle nose pleco, 3 female mollies (two of which are his daughters), 2 male guppies, 4 baby mollies, and 6 tetras. Around 3 weeks ago I saw him sitting at the bottom of the tank barely moving. The day before he was super active and trying to mate like always. I did a water change and also reduced feeding by 30% in case it was due to overfeeding. I also fed some green peas to all the fish and put some salt in the aquarium. A few days later he wasn't on the floor anymore but now he stays almost always at the top of the fish tank and doesn't even bother to go near the females which he always used to do. There's enough oxygen and I don't think he's eating biofilm. The other fish do not exhibit any of the strange behaviours of the male molly. Could it be an illness? Currently, I am using Tetra Lifeguard to see if he gets back to normal but I am only using it at 75% potency relative to dosage for my tank size. (Re-uploaded but removed the previous thread due to no reply and the wrong thread)

Info:
Tank is cycled
Fish have been in 20 gal for 4 months but I've had them for 1 year+
Nitrite, Ammonia, and Nitrate levels are all at 0
The GH is 150ppm - 175ppm
HK is 160ppm
Ph is 7.5
Chlorine is 0.
I have an airstone for oxygen
I Feed 2x a day
I also use a filter that goes up to 35 gallons.
The male is around 1.5 - 1.75 years old.
I have 6 natural plants (one is growing fast)
I have 4 Decorations (one xl, one large, and two medium)
I change the water every 2 weeks 35% I clean the decor, filter, and substrate
The week within I do a small 15% but do not clean substrate or decor, only the filter.
I use liquids/supplements like Seachem Prime, API stress coat, and Seachem Flourish along with Big Al's water conditioner and Big Al's bio support. I use them every week but put 1/2 - 3/4 of all doses during the week of the 15% water change and the full amount the week of the 35% water change.
I have a black sponge filter in addition to the mechanical filter

Additional Question
Why does my female molly do this? She has done this almost since we first got her. She has never been sick and she is currently healthy. She does it a few times per day.

 

[Fishfunn]

I use liquids/supplements like Seachem Prime, API stress coat, and Seachem Flourish along with Big Al's water conditioner and Big Al's bio support. I use them every week but put 1/2 - 3/4 of all doses during the week of the 15% water change and the full amount the week of the 35% water change.

• First, you are adding too many additives to your water. Just use Prime to dechlorinize water only. Using API Stress Coat is overkill, plus it adds more stuff that can cause your fish grief. Your fish have a natural slime coat, and adding API stress coat is not needed. If you really need to add Seachem Flourish, do so sparingly. In my established tanks, I never need or use liquid fertilizer. The fish waste has more fertilizer than I need. I only used Flourish root tabs for established rooted plants. Depending on the size of the plant dictates if I use root tabs or not.
• Dont overclean your filters. It takes time for them to recover the valuable nitrification bacteria to keep your fish healthy. I clean my filters only when I notice reduced water flow by getting clogged. When I clean them, I only clean in used aquairum water to rinse the muck out that is causing blockage. I never have to add bottled bacteria to my tanks again once the filters have cycled.
• Make sure when you do a water change, the added water's temperature is at the same tank water temperature or a little higher. Adding cooler water to the tank will temperature shock your fish and cause an Ich breakout.