Originally Posted by Bradman
I dont know the GH, PH, ammonia,nitrite, and nitrate levels. I dont have the test kit. I know i should know this but like i said Im still new to this. Helping me out is the best way for me to learn
The GH of your tap water is not likely to change in the aquarium, so check your municipality's water supply website. It should mention general hardness or total hardness. Might also have pH. If you can't figure it out, which sometimes happens, post the link and I'll take a look.
The reason I am pushing this is that livebearers need moderately hard water, and molly are especially susceptible to softer water. Tetra on the other hand are soft water fish. There is some degree of tolerance, but as this trouble is with the molly, I'd like to be certain the water is suited for them, or not as the case may be. Stress caused by water parameters being off even a bit will weaken fish, making them more susceptible to other health issues.
Ammonia, nitrite and nitrate is worth checking esp in new tanks. A good investment is the API liquid Master Test Kit. It has pH, ammonia, nitrite and nitrate, all you need. It maybe less expensive online, so consider that.
On the deaths, the higher temp and adding water circulation via the airstone/bubbler is good. I just like to know the above in case we have other issues factoring in. We all learn, sometimes by losing fish.
But don't be discouraged.