How many pellets you guy feeding him with?
If he got bloated right after you fed him then of course he can be bloated because of it. I am wondering how many pellets you gave him. I know this kind of the pellets they kind of bigger than other brands.
I don't think that epsom salt will make him pale. Did his behavior changed? How he doing now?
Also what can stress him out that if you didn't acclimate him. When you change him make sure new water temperature the same and take time acclimate to the temperature/chemistry. Just keep adding new water in his changing cup for about 3 times and let him sit in it for about 5 min each time when you do it. Did he get pale right after water change?
Did you use unscented epsom salt?