After several years my 3 rhododendrons,white, red and lilac have now all become white. Might they need special fertiliser ?
Look up 'Cunningham's White' and see if any of them are that variety. Which has been used as a rootstock in the past - for a time hybrid rhododendrons were all grafted instead of grown from cuttings. So that older plantings often consist of mixtures of various colors in combination with shoots made by roostocks which have been unknowingly allowed to grow up and mix with, even overwhelm the kinds grafted onto them. Commonly Rhododendron ponticum rootstock is seen doing this. But again there was some use of 'Cunningham's White' also.
Many thanks and sorry it took so long to reply. Unfortunately it is over 30 years that we had planted them and I dont have any info on what variety they are.