Hi,
I am not sure if this is a problem – but here goes:
We planted a lot of tulips over the past two years in the garden and they are all fantastic specimens – even if we have to say so ourselves – especially after a trip to the Keukenoff Gardens in Amsterdam last year. These tulips are doing well.
BUT – several years ago we bought 100 each of red and yellow tulips in Lidl when they had them. Now – these specific tulips go in containers and are the only ones lifted every year. Last year a lot of them seemed to have crossed – i.e. red and yellow in some, and the other half was paranoid and burned some of them. Now the ones we have left are flowering – some of them are red, some are yellow, some are pink, yellow with a green back, and the colours do not seem to be as striking in others.
Is this clearly a case of tulip fire? Do we burn them all?
Or do tulips over time just fade anyway?
 This is not tulip fire which is a fungal disease that causes withering of a few bulbs, just as though they had been burned, and which spreads to other plants later, and produces grey mould growth on the affected parts in wet conditions.
Leave your old yellow and red kinds be, unless you thinkt he degree of streaking and colour change is exccessive because virus can be transferred to other tulips by sap-sucking insects.