cucumbers

I sowed my cukes (various outdoor types) about a month ago and they're doing well on the window-sill.
I always water from the bottom to avoid stem rot but I noticed today that the strong root formation is causing tiny white rootlets to break the surface of the compost.
I thought it was some kind of mycelium and had a rootle (not much.....we all know how suicidal cukes are!) but I'm sure it's rising rootlets.
Is this a sign to re-pot? I assume I must be VERY careful when repotting.......

I agree, it outgrew it's little home. Replant at the same depth but in a bigger pot.