Betta with growth

[youaremyjoy]

I have a crown tail Betta male, approx 1 year old. He is kept in a 5 gallon planted tank that is cleaned 25% weekly. Up until the last 2 weeks, he's been doing great, still acting fine, just has a mass. Two weeks ago I noticed a small black bump on his back. In the last few days is has grown rapidly and now has hard white spots on it. There are 5-6 pink rams horn snails in the tank. I quarantined them for 4 weeks prior to introducing them.
Any thoughts/suggestions?
Temp 79
pH 7.0
Ammonia 0
Nitrite 0

Joanna

 

[youaremyjoy]

After doing some additional homework, I am thinking this is likely lymphocystis.
I have 4 other Betta tanks, how should I disinfect my gravel cleaner tubing? Or can I?