First off can you give a bit more detailed information. Not sure what 'smooshed' is. How old is your betta? Brand new? (older bettas find often start to curl).

Here is a great site and this aspect shows bettas with most commmon diseases including fin rot.

http://bettatalk.com/betta_diseases.htm

Tips of fin white and blue. (fin rot usually black brown, reddish so on). Hard to spot sometimes depending on natural coloration of fish. That said, when you say white, meaning white pigment or white fuzz or patchy?

What size container, heated (needs to be in pretty steady temp range about 80) Plants, they love the security of plants and a great one for single betta is any of the smaller anubias. They can grow in almost any condition and low light. Bettas come from (for the most part some are from streams) heavily planted slow moving or stagnant waters and are stressed in higher direct lighting and worse with no hiding place (little cave such as coconut hut or similar) or plants. Anubias don't need sand as well.

So what size and if smaller then 2.5 gallons that is stressful to begin with. At 2.5 gal you can use the smaller suction cupped filter with air valvue to slow down the water/air flow. (too rapid water air flow is a stress factor).

They like a pinch of salt (I found aquarium raises ph, so use kosher salt, pure salt and nothing else).

Now, when doing water changes. Again, depending on the size (check betta site above to see diff sizes and water changes)... if small more then once a week is needed esp with no filter (another reason for a filter).

Try not to scrub out all of the cultured bacteria which will be on the walls, another reason for having a plant, as they will be on that surface and help to keep these cultures going.

I find this system keeps my betta pretty stress free.

I lower the lights, and use a plastic container to gentle scoop him out with full water, less about 1/2 inch so he can come up for air. I cover him with plastic (larger then tub) lid with smaller holes in it, then put towel around his container and over lid (little bit open so I can watch him).

I've already prepared the water with same ph and temp.

I clean and fill his tank (2.5 long) but do not replace filter cartridges (or cycling will restart) (I replace filter cartrige on non water change days). This is a full change, and depending on water conditions, sometimes I syphon off bottom (which I do usually twice a week as this betta misses his food and does not bottom feed as some do) and refill.

Then I put the tub in a larger bowl, and start dribbling with small air hose (can tie in knot and adjust for flow rate) the new water into his tub, and use a turkey baster to take it out. When it is pretty much replaced, ie clean water mostly in his plastic container (and another reason for hole in lid, ie put air tubing through it) I (keep lid on as this stressed time is often when they jump) place tub back in tank (lights still off or low) and tip it to let him swim out. After a bit I gradually raise light (low watt at that).

There are variations on this depending on what change is needed. Sometimes I syphon bottom and dribble fresh water over his tank. I do it slowly as bettas get stressed with any changes.

Hope this helps. Best Sherry

As you can see with this bettatalk link there are many different ways of betta care. I found what I do less stressful for my bettas, which are already stressed coming from little cold dirty bowls from local petsore and last one not sold.
http://bettatalk.com/betta_care.htm