Yes there is. You can try boiling your water. The mineral deposits will calcify and create scales will separate from your water. This is a process will take a while but may work. It's time consuming due to the size tank you have but its inexpensive.
Boiling only removes the KH part of hardness not the GH. The only way to soften water is to dilute it with water of a lesser softness like rainwater or RO water. Betta are very adaptable, and messing with hardness can be very tricky. With something as sensitive as a baby betta, you could easily do more harm than good.
I agree that the neons should be re-homed. They like softer water and also need groups of 6 or more other neon tetra around. Without this they can be very nasty to your betta. The platies will do fine in water that is hard, but they need a larger tank as they grow.
I probably would relocate the neon tetra but I really don't have anywhere to put them also they look okay in there to me. Collecting rain water would be good but that's not really possible in iowa right know because there has barely been any rain for mor than a month or two. Although one does look like it has a numb on its belly I'll post a pic of that in the morning.
Driftwood, specialized substrates, peat in the filter... Those are the safest way to lowest hardness a bit. Rain water can have acid in it or other pollutants, and RO water leaves zero essential minerals, you should add a product to restore important nutrients that won't raise the hardness.
Are any of the fish having problems....generally all those species will tolerate hard water without issue, however, with the Neon you can usually keep them in hard water but you will need to soften the water if you want to spawn them since their eggs usually will not hatch or fry develop in hard water.
I have really hard water with a high pH...The KH/GH over 300 and pH 8.6 and it has never been an issue with my Neon tetra, but I do have to change the softness when I spawn them and I have to keep the egg and fry in the softer water for the first 30-50 days then I will slowly acclimate them back to my hard water.