Hello. I am an artist..a painter in Bethnal Green

I have had mould appearing on the backs of my large paintings. The humidity must have find up in here over a period of time. I have stored the paintings here in the same way since 2002 when a damp course was put in. But something has changed. From Jan until May there was a bad leak from the gutter which cause rain water to pour down outside my window ...for 5 months whenever it rained. Now there is efflorescence on the inside wall near to where that leak was outside. What I would like to know is if that leak could have caused the mould situation to develop. Where there is efflorescence there is moisture I have read. A basement will always be more humid of course but J had no sense of it being damp at all. Finding the mould on the work was a big shock. Thanks for any view you might have.