Thank you for your reply!
The tank water pH is 6.9, TDS 90.
We use a heater and the temperature is 89.6F.
We do have medication: Artemiss and ParaGuard (picture attached).
We have had the betta fish for a year, Otocinclus for more than 4 months, shrimps for more than 6 months and the horn snail and the black snail for 3-4 months.
Please find pictures of the whole setup attached.