Old bulbs question

[Mattl22]

So I defiantly need to replace my bulbs in my mh fixture but am trying to wait till Christmas because it's gonna cost over 200$ to replace them all

So question about old bulbs can they cause or help hair algae grow?

What is my best choice for new bulbs for double ended mh I'm thinking of 10k because I'm in a grow out stage or would 12 k be better choice also what brand do u recommend ?

My fixture has 2 double pc bulbs 1 pink 1 blue do these need to be replaced also?

Thanks for any help / recommendations
Matt