This flat roof is on a kitchen extension from the mid 1990's. I have noticed three small mould patches close together recently which are at the opposite end of the skylight (north of it). I also have mould where a skylight is which has been there at least a year. I can't see any major issues from the bedroom window apart from obvious blistering of the felt. Some questions: Can a liquid rubber be applied to maintain it before a refelt? Can the skylight be resealed? Is it save to go on this type of roof after all these years? Many thanks.