Just let it be for now Matt. I have six different bamboos and the Phyllostachis ones in particular have been hard hit this winter. 4 of them are brown but if I examine closely there are signs of what the politicians would call 'the green shoots of recovery'.

Keep watering and feeding Bamboo. The main growth season is June. My new Bamboo plantings (Fargesia murielae) are doing well, but my neighbours' Phyllostachis is looking very brown and dead - it has lost a lot of height and leaves. I can see some greenness under the brown, so please wait till June/July for lots of green to show.

i dress my bamboo ie below a certain hight i take all the thinner shoots and leaves of forcing it to grow the thicker better looking shoots up . possibly not yet while its down just as the others say lots of water . bamboo doesnt grow like other plants . hgowever thick it starts out growing as a shoot it will stay egsactly that width just get taller .