Just a thought, mollies are very prone to Ich unless kept in very warm, almost brackish water, (especially the mass produced ones shipped to LFSs, and are bought cheap), so quarantining them for at least a month would be prudent.
You may have been lucky so far but all it takes is one cyst, and your prize fish can end up like this.

You may have been lucky so far but all it takes is one cyst, and your prize fish can end up like this.
