Help! My Betta is sick!

[Jeana721]

I've had my Betta fish for about 6 months now and he was a happy healthy Betta who used to make some pretty awesome bubble nests. He lives in a 5.5 gallon tank with nerite snails and live plants. I recently did about a 40% water change and bought a new filter because the old one broke. The filter is an elive brand for small tanks. The current from the new filter was way too strong so I modified it by putting a small piece of fish netting in the spray bar. After the water change Mr. Miyagi seemed to be staying at the bottom of the tank and just didn't seem like himself. The next day my girlfriend unknowingly changed almost all of the water thinking that the water was the problem. Its been 3 days now and Mr. Miyagi is still acting quite sluggish, not building bubble nests, not eating much, looks a little lighter in color, and generally just not himself at all. I noticed his scales sticking out a bit and thought it could be dropsy, but he doesn't look bloated at all. Also, after the water change all of the snails crawled out of the water to the top of the tank. Now the snails are all in the water but one and none are really moving around. The water temp is 84, the pH 8. I have not tested ammonia and nitrates but use a water conditioner for that. What happened? What can I do?